186 F.3d 1119 (9th Cir. 1999)
UNITED STATES OF AMERICA, Plaintiff-Appellee,v.CHRISTOPHER MCIVER, Defendant-Appellant.UNITED STATES OF AMERICA,  Plaintiff-Appellee,v.BRIAN EBERLE, Defendant-Appellant.
No. 98-30145  No. 98-30146
UNTED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT
Argued and Submitted February 2,1999Filed August 6, 1999

[Copyrighted Material Omitted][Copyrighted Material Omitted]
Bruce Gobeo, Gobeo Law Offices, Missoula, Montana;  Doreen Antenor, Bailey & Antenor Law Offices, Missoula,  Montana, for the defendants-appellants.
Kris McLean, Assistant United States  Attorney, Missoula, Montana, for the plaintiff-appellee.
Appeals from the United States District Court for the District of Montana  Donald W. Molloy, District Judge, Presiding. D.C. No. CR-97-00058-2-DWM.
Before: Arthur L. Alarcon, Pamela Ann Rymer, and Andrew J. Kleinfeld, Circuit  Judges.
OPINION
ALARCON, Circuit Judge:


1
Christopher McIver ("McIver") and Brian Eberle  ("Eberle") appeal from the judgment entered following their  conviction by a jury for conspiracy to manufacture marijuana  in violation of 21 U.S.C. S 841(a)(1).


2
We must decide for the first time whether the placing by  law enforcement officers of a magnetized electronic tracking  device on the undercarriage of a vehicle is an unreasonable  search and seizure.


3
McIver and Eberle contend that the district court erred in  denying their motions to suppress evidence, in ruling on their  objections to the admissibility of evidence, and in its instructions to the jury. They also argue that the evidence was insufficient to support their conviction, and that the district court  erred in its sentencing decision.


4
We affirm because we conclude that the district court did  not err in rejecting each of these contentions.


5
* Factual Background


6
The evidence at trial viewed in the light most favorable to  the Government revealed the following facts:


7
On or about July 8, 1997, United States Forest Service officers at the Kootenai National Forest became aware that six  transplanted marijuana plants were being cultivated in a grow  site in the Sunday Creek area. These plants were destroyed by  members of the Northwest Drug Task Force because they did  not have the resources to conduct a surveillance.


8
On July 30, 1997, Special Agent Lorney Jay Deist received  a report from a United States Forest Service hydrologist that  he had observed a marijuana plant growing in the same site  in the Sunday Creek area. Special Agent Deist was the supervisor of ten Forest Service law enforcement officers assigned  to the Kootenai National Forest.


9
On the same date, Special Agent Deist and Forest Service Law Enforcement Officer Joel Young accompanied the  hydrologist to the Sunday Creek area. The officers found four  marijuana plants. Special Agent Deist assumed from the quality of the plants that the person who was growing them had  planted similar gardens in the immediate area. Special Agent  Deist observed that the marijuana plants had been transplanted because the soil around them was not from that area. The area was tilled to receive the plants and had been  amended with peat moss and fertilizer.


10
Special Agent Deist determined that because he had only  ten law enforcement officers under his command, it would not  be feasible to station them to conduct a surveillance of the site  in order to learn the identity of the persons responsible for  growing the plants. Instead, on August 1, 1997, he installed  video and still cameras to photograph persons who  approached the area where the plants were growing. The  unmanned cameras were motion activated.


11
Among the vehicles photographed at the site was a white  Toyota 4Runner truck. The Toyota 4Runner had unique pink  spots on the side. On or about August 17, 1997, McIver was  photographed near the marijuana plants accompanied by a  person with dark hair. On September 12, 1997, McIver was  photographed bending over the marijuana plants, and holding  a camera near the plants. On September 18,1997, Special  Agent Deist observed a Toyota 4Runner that looked similar  to one photographed by one of the Sunday Creek surveillance cameras. He followed the Toyota 4Runner to the Burlington  Northern Roundhouse. The vehicle was parked in the employees' parking lot. When the driver stepped out of the vehicle,  Special Agent Deist observed that he looked very similar to  one of the persons captured on film at the Sunday Creek marijuana garden. Special Agent Deist traced the registration of  the vehicle through law enforcement channels from its license  plate. It was registered to Christopher McIver, whose residence was listed at 844 1st Avenue West, Kalispell, Montana.  On September 19, 1997, a person wearing a long ponytail hair  style was photographed near the marijuana plants.


12
After obtaining this information, Office Deist drove to  McIver's residence. There, he observed a maroon Chevy  Nova. By tracing its license number, he learned that it was  registered to Brian Eberle, whose residence was listed as 844  1st Avenue West, Kalispell, Montana. An officer who had the  residence under surveillance noted that Eberle wore a long  ponytail, and that he drove the Chevy Nova.


13
During the last half of September, 1997, Special Agent  Deist noticed that the buds on the marijuana plants in Sunday  Creek had matured. He was aware from his prior training and  experience that frost makes the THC substance in marijuana  more active and "go to the bud." When that occurs, it is time  to harvest the plant. Because the buds had matured, Special  Agent Deist concluded that the marijuana plants at Sunday  Creek would be harvested after September 23, 1997.


14
At 3:30 a.m. on September 23, 1997, Special Agent Deist  and Officer Billy Stewart placed two magnetized tracking  devices on the undercarriage of the Toyota 4Runner registered  to McIver. One of the devices was a global positioning system. The other was a Birddog 300 electronic transmitter that  sends a weak signal or a "beep" to an audio unit ("monitor")  installed in the officer's vehicle. When the monitoring vehicle  gets close to the transmitter, the signal received in the audio  unit becomes stronger. The monitor also contains a 180  degree dial with a needle that points in the direction of the  transmitter. When the tracking devices were placed on the  Toyota 4Runner, it was parked in the driveway in front of  McIver's garage, outside the curtilage of the residence.


15
The global positioning system malfunctioned after three  days. Using the monitor, the officers tracked McIver from  September 23, 1997 to October 2, 1997 as he traveled from  his home to the Burlington Northern Roundhouse.


16
On October 2, 1997, United States Forest Service Law  Enforcement Officer Keith Granrud observed the Toyota  4Runner leave the residence at approximately 8:40 p.m. Officer Granrud notified Special Agent Deist.


17
Special Agent Deist directed Officer Young to station himself near the intersection of Highway 93 and the Radnor  Creek access road to the Sunday Creek area. Special Agent  Deist then proceeded to Highway 93. Using the monitor, he  located the Toyota 4Runner driving north on Highway 93 towards the Radnor Creek junction. At 9:30 p.m., Officer  Young observed the Toyota 4Runner turn off on the Radnor  Creek access road. Special Agent Deist and Officer Young  drove north of the Radnor Creek turn-off to a location within  a mile of the Sunday Creek site.


18
By monitoring the signal from the Birddog 300 electronic  tracking device, the officers determined that the Toyota 4Runner was in the vicinity of the marijuana garden. The officers  returned to the Radnor Creek turn-off for Highway 93.


19
The video surveillance cameras photographed two persons  harvesting the marijuana plants and stuffing them into shiny  plastic bags. At 10:30 p.m., the monitor received a new signal  from the Birddog 300 electronic tracking device indicating  that the Toyota 4Runner was moving. At 10:35 p.m., the officers observed the Toyota 4Runner turn onto Highway 93 and  head south towards Kalispell.


20
Special Agent Deist directed Officer Young to check the  marijuana plants to determine their present condition. Officer  Young discovered that each of the plants had been pulled out  from the ground or cut off near ground level. Special Agent  Deist alerted Officer Stewart, who was on surveillance duty  at the McIver/Eberle residence that the Toyota 4Runner  appeared to be returning to that location.


21
From an alley opposite the McIver/Eberle residence, Officer Stewart observed the Toyota 4Runner drive up and park in front of the garage at 11:50 p.m. Officer Stewart observed  that McIver was the driver and Eberle was his passenger.  McIver and Eberle removed large plastic bags from the back  of the Toyota 4Runner. The bags were bulky. Stems or rods  protruded from the top. McIver and Eberle carried the bags  into the house.


22
At approximately 12:30 a.m., the officers, led by Special  Agent Deist, entered the McIver/Eberle residence without a  warrant. Eberle and McIver were arrested. The officers conducted a protective sweep of the residence for weapons or  cohorts of the arrestees. They observed in plain view cut marijuana and firearms in one bedroom, and a sophisticated grow  operation in the basement - including 63 marijuana plants,  potting soil, fans, heat lamps, and chemical sprays.


23
After the protective search, the house was sealed off until  a search warrant could be obtained. A search warrant was  executed at the McIver/Eberle residence at 1:00 p.m. on October 3, 1997. The officers seized the marijuana plants they had  previously observed during the protective sweep of the house.


24
On the morning of October 3, 1997, several officers  returned to the Sunday Creek site and removed what remained  of the marijuana plants. This evidence was introduced at trial.


25
The Toyota 4Runner was impounded. On October 4, 1997,  it was subjected to an inventory search. Evidence seized during the search and admitted at trial included a small quantity  of marijuana leaves, a green bamboo plant stake, McIver's wallet, and a pair of sunglasses similar to those worn by  McIver in several surveillance photographs.


26
A federal grand jury indicted McIver and Eberle on one  count of conspiracy to manufacture marijuana, and one count  of possession of marijuana with intent to distribute. During a  pre-trial suppression hearing, the district court ruled that the  warrantless entry of the McIver/Eberle residence violated the  Fourth Amendment. The court suppressed the evidence  observed following the entry, including the 63 marijuana  plants seized from the basement the next day pursuant to the  search warrant.

II
Discussion

27
We discuss each of the issues raised by McIver and Eberle,  and the facts pertinent thereto, under separate headings.


28
A. Warrantless placement of unmanned surveillance cameras on national forest land


29
McIver and Eberle contend that the district court erred in  not granting their motion to suppress the photographs  obtained by the Forest Service Officers through the use of  unmanned still and video cameras without a warrant. We review de novo the lawfulness of a search and seizure. See  United States v. Hudson, 100 F.3d 1409, 1414 (9th Cir. 1996),  cert. denied, 118 S.Ct. 353 (1997). The trial court's underlying factual findings are reviewed for clear error. See id.  Whether an individual has a reasonable expectation of privacy  in an area that has been searched is a question of law we  review de novo. See United States v. Fultz, 146 F.3d 1102,  1104 (9th Cir. 1998).


30
The Supreme Court has instructed that:  The touchstone of Fourth Amendment analysis is whether a person has a "constitutionally protected reasonable expectation of privacy." Katz v. United States, 389 U.S. 347, 360 (1967) (Harlan, J., concur ring). Katz posits a two-part inquiry: first, has the individual manifested a subjective expectation of privacy in the object of the challenged search? Second, is society willing to recognize that expectation as reasonable?


31
California v. Ciraolo, 476 U.S. 207, 211 (1986).


32
McIver and Eberle maintain that the placement of  unmanned cameras in a remote area of a national forest without a search warrant violated their reasonable expectation of  privacy. They cite no authority that supports this novel proposition.


33
McIver and Eberle were on public land in a national  forest when they cultivated their marijuana garden. Thus, they  knowingly exposed their illegal activities to any person who  visited that area. McIver and Eberle conceded that the observation of the marijuana plants by the Forest Service officers  did not violate their Fourth Amendment rights. Clearly, the  Forest Service officers had a right to carry out their law  enforcement duties in each area of the Kootenai National Forest. It is also beyond dispute that the Forest Service could  have stationed officers to conduct a 24-hour surveillance of  the marijuana garden. See Oliver v. United States, 466 U.S.  170, 178 (1984) (holding that individuals "may not legitimately demand privacy for activities conducted out of doors  in fields, except in the area immediately surrounding the  home").


34
McIver and Eberle argue that the use of an unmanned  camera, as opposed to a camera operated by a Forest Service  officer, constitutes an unreasonable search in violation of the  Fourth Amendment. In United States v. Knotts, 460 U.S. 276  (1983), the Court held that "[n]othing in the Fourth Amendment prohibited the police from augmenting the sensory faculties bestowed upon them at birth with such enhancement as  science and technology afforded them." Id.  at 282. In United  States v. Dubrosky, 581 F.2d 208 (9th Cir. 1978), we stated:


35
Permissible techniques of surveillance include more than the five senses of officers and their unaided physical abilities. Binoculars, dogs that track and sniff out contraband, searchlights, fluorescent powders, automobiles and airplanes, burglar alarms, radar devices, and bait money contribute to surveil lance without violation of the Fourth Amendment in the usual case.


36
Id. at 211. We reject the notion that the visual observation of  the site became unconstitutional merely because law enforcement chose to use a more cost-effective "mechanical eye" to  continue the surveillance. See Knotts, 460 U.S. at 284  ("Insofar as respondent's complaint appears to be simply that  scientific devices such as the beeper enabled the police to be  more effective in detecting crime, it simply has no constitutional foundation. We have never equated police efficiency  with unconstitutionality, and we decline to do so now."). We  conclude that while McIver and Eberle may have anticipated  that cultivating marijuana in a remote area of a national forest  would not be observed by law enforcement officers, they have  failed to demonstrate that they had an objectively reasonable  expectation of privacy in their cultivation of marijuana in an  area open to the public. We are also persuaded that the use of  photographic equipment to gather evidence that could be lawfully observed by a law enforcement officer does not violate  the Fourth Amendment. The use of a motion activated camera  under these circumstances appears to us to be a prudent and  efficient use of modern technology.


37
Our holding on this issue is quite narrow. Illegal activities  conducted on government land open to the public which may  be viewed by any passing visitor or law enforcement officer  are not protected by the Fourth Amendment because there can be no reasonable expectation of privacy under such circumstances. We are mindful that a person can have a reasonable  expectation of privacy in a hotel room, a cabin, or an enclosed  tent on public lands. See, e.g., United States v. Gooch, 6 F.3d  673, 677 (9th Cir. 1993) (holding that a person has a reasonable expectation of privacy in a tent pitched in a public campground). In Katz v. United States, 389 U.S. 347, 351-52  (1967), the Supreme Court explained that what a citizen  "seeks to preserve as private, even in an area accessible to the  public, may be constitutionally protected." Here, McIver and  Eberle did not conceal their marijuana garden. As they have  conceded, other persons visited the same area and were photographed by the motion activated cameras.


38
B. Legality of the warrantless placement of the electronic tracking devices on the Toyota 4Runner McIver argues that the act of placing the electronic tracking  devices on the undercarriage of the Toyota 4Runner constituted an unreasonable search and seizure. He does not contend  that the officers infringed his Fourth Amendment rights by  monitoring the beeper as the Toyota 4Runner traveled on the  streets and highways. He forthrightly cites United States v.  Knotts, 460 U.S. 276 (1983), for the proposition that there is  no reasonable expectation of privacy while on a public thoroughfare. Instead, he asserts that the district court erred in  denying his motion to suppress "all evidence gathered as a  result of the tracking devices."


39
McIver first maintains that a search warrant was  required because the officers committed a trespass by placing  the electronic tracking devices on the undercarriage of the  Toyota 4Runner while it was parked in his driveway. McIver  concedes that the Toyota 4Runner was outside the curtilage.  The record shows that the driveway and the apron in front of  the garage were open to observation from persons passing by.  The driveway was not enclosed by a fence and a gate.


40
In Oliver, the Court stated that "only the curtilage, not  the neighboring open fields, warrants the Fourth Amendment  protections that attach to the home." 466 U.S. at 180. The  court also opined that "[t]he law of trespass, however, forbids  intrusions upon land that the Fourth Amendment would not  proscribe. For trespass law extends to instances where the  exercise of the right to exclude vindicates no legitimate privacy interest." Id. at 183. Assuming arguendo that the officers  committed a trespass in walking into McIver's open driveway, he has failed to demonstrate that he had a legitimate  expectation of privacy cognizable under the Fourth Amendment in this portion of his property.


41
Secondly, McIver contends that the mere placement of  the electronic tracking devices on the undercarriage of the Toyota 4Runner was an illegal search and seizure. "We must  first determine whether this can be considered a`search' subject to the Fourth Amendment -- did it infringe an expectation of privacy that society is prepared to consider reasonable?" United States v. Jacobsen, 466 U.S. 109, 122  (1984). In New York v. Class, 475 U.S. 106 (1986), the Court  held that there is no reasonable expectation of privacy in the  exterior of a car because "[t]he exterior of a car, of course, is  thrust into the public eye, and thus to examine it does not constitute a `search'." Id. at 114 (citing Cardwell v. Lewis, 417  U.S. 583, 588-89 (1975)). In Class, the officer's conduct in  opening the door of the respondent's car to move papers that  obscured the vehicle's identification number ("VIN") located  on the dashboard was held not to violate the Fourth Amendment. See id. at 107. The court reasoned that "[t]he VIN's  mandated visibility makes it more similar to the exterior of  the car than to the trunk or glove compartment." Id. at 114.  Relying in part on the Supreme Court's opinion in Class, the  Tenth Circuit held in United States v. Rascon-Ortiz, 994 F.2d  749 (10th Cir. 1993), that "[t]he undercarriage is part of the  car's exterior, and as such, is not afforded a reasonable expectation of privacy." Id. at 754. In Rascon-Ortiz, an officer  "knelt down and looked under the car with a flashlight." Id.  at 750. Here, rather than making a visual inspection of the  undercarriage of the Toyota 4Runner, the officers placed the  magnetized electronic devices on the vehicle's undercarriage.  In determining whether the officer's conduct was a search, we  must decide whether McIver has demonstrated that he  intended to preserve the undercarriage of the Toyota 4Runner  as private -- free from warrantless governmental intrusion.  McIver did not produce any evidence to show that he intended  to shield the undercarriage of his Toyota 4Runner from  inspection by others. Furthermore, in placing the electronic  devices on the undercarriage of the Toyota 4Runner, the officers did not pry into a hidden or enclosed area.


42
At oral argument, McIver argued that the placing of the  electronic devices on the undercarriage of the Toyota 4Runner  was a seizure of the vehicle. This argument ignores the principle articulated by the Supreme Court in United States v. Karo,  468 U.S. 705 (1984). There, the Court wrote:


43
A "seizure" of property occurs when "there is some meaningful interference with an individual's possessory interests in that property." [citing Jacobsen, 466 U.S. at 113]. Although the can may have contained an unknown and unwanted foreign object, it cannot be said that anyone's possessory interest was interfered with in a meaningful way. At most, there was a technical trespass on the space occupied by the beeper. The existence of a physical trespass is only marginally relevant to the question of whether the Fourth Amendment has been violated, however, for an actual trespass is neither necessary nor sufficient to establish a constitutional violation.


44
Id. at 712-13.


45
McIver did not present any evidence that the placement  of the magnetized tracking devices deprived him of dominion  and control of his Toyota 4Runner, nor did he demonstrate  that the presence of these objects caused any damage to the  electronic components of the vehicle. Under these circum- stances, we hold that no seizure occurred because the officers  did not meaningfully interfere with McIver's possessory interest in the Toyota 4Runner.


46
C. Admissibility of evidence seized from McIver's Toyota 4Runner


47
Prior to trial, McIver and Eberle moved to suppress all evidence found in their house by law enforcement. The district  court ruled that the warrantless entry into the house at 12:30  a.m. on October 3, 1997 was not justified by exigent circumstances, and was therefore unlawful. The district court applied  the "fruit of the poisonous tree" doctrine and ruled that the  evidence seized in the house pursuant to a search warrant on  the afternoon of October 3, 1997 was inadmissible to prove  guilt. The Toyota 4Runner was also seized pursuant to the  search warrant. It was towed to a Forest Service impound lot.  On October 4, 1997, it was subjected to an inventory search.  The officers seized a pair of Oakley sunglasses that were on  the dashboard, green leafy material from the passenger seat,  a green bamboo plant stake, and a wallet containing McIver's  driver's license.


48
Prior to jury selection, the Government informed the court  that it intended to offer the evidence seized from the Toyota  4Runner. Defense counsel objected on the ground that the evidence seized from the Toyota 4Runner was the "fruit of the  poisonous tree."After reviewing the affidavit and the application for the  search warrant, the court denied the motion to suppress the  evidence seized from the Toyota 4Runner. The court reasoned  that after excluding all facts alleged in the affidavit and the  application that were gained from the warrantless entry into  the residence, sufficient circumstances were alleged based on  the information gathered prior to the entry to establish probable cause to issue the warrant for the seizure of the truck.


49
Before this court, McIver maintained that the district court  erred in admitting the evidence seized from the Toyota 4Runner because it was the fruit of an illegal search of the house  conducted prior to the issuance of the search warrant. We  review de novo a district court's determination that probable  cause existed for the issuance of a search warrant. See United  States v. Hernandez, 80 F.3d 1253, 1258 (9th Cir. 1996).


50
We have examined the affidavit in support of the search  warrant. It contains sufficient facts independent of those  obtained from the officers' observations after their entry into  the house to demonstrate probable cause for the search of the  Toyota 4Runner.


51
Special Agent Deist's affidavit contained the following  facts: A hydrology crew discovered what they believed to be  a marijuana plant in the Sunday Creek drainage in the Kootenai Forest. The hydrologists removed a leaf from the plant.  They reported their observation to Forest Service law enforcement officers. The leaf was tested. It was marijuana. Forest  Service law enforcement officers went to the site with the  hydrologists on July 30, 1997. They found three additional  plants.


52
Motion activated surveillance cameras installed at the site  showed that a white Toyota 4Runner was at the Sunday Creek  site on August 17, 1997 and September 12, 1997. On September 18, 1997, Special Agent Deist observed the same vehicle  on U.S. Highway 93. Special Agent Deist followed the vehicle to a Burlington Northern parking lot. The driver was the  same person depicted in the photographs taken at the Sunday  Creek site. A check of the vehicle's registration based on the  license plate number disclosed that McIver was listed as the  owner and that he resided at 844 1st Ave. West, Kalispell,  Montana. Special Agent Deist also determined that McIver  was employed by Burlington Northern and was currently  working in the Sunday Creek area.


53
On September 22, 1997, a Birddog 300 electronic tracking  device was placed on the Toyota 4Runner. On October 2,  1997, a surveillance officer observed the Toyota 4Runner  leave the McIver/Eberle residence and proceed north. Special  Agent Deist followed the vehicle to the turnoff on Radnor  Road to the Sunday Creek area.


54
Special Agent Deist followed the Toyota 4Runner when it  returned to Highway 93. Meanwhile, Officer Young inspected  the Sunday creek site and observed that two of the marijuana plants had been harvested. The same officer had seen the  plants untouched that same morning.


55
Officer Stewart observed the Toyota 4Runner return to the  McIver/Eberle residence at 11:50 p.m. Using night vision  equipment, he observed McIver and Eberle remove two large  plastic bags from the back of the vehicle. The bags were full  and contained plant stems.


56
These facts amply demonstrate that probable cause  existed to believe that the Toyota 4Runner was used to transport marijuana plants and that it might contain evidence of a  crime. The district court did not err in denying the motion to  suppress the evidence found in the Toyota 4Runner.


57
D. Admission of the photographs and videotapes into evidence


58
Eberle asserts that the district court erred in admitting the  videotapes and still photographs because they were not properly authenticated or identified as required by Rule 901(a) of  the Federal Rules of Evidence. The record shows that Eberle's  counsel informed the court that therewould be no objection  to the photographs marked as Exhibits 4 through 25.


59
Officer David Helmrick installed the cameras at the Sunday  Creek site. His testimony was offered to lay the foundation  for the admission of the still photographs and the pictures on  the videotapes. He testified that Exhibit 26 was an edited video tape containing all the activity around the marijuana  plants and the adjacent parking area captured by the video  surveillance cameras. It was referred to at trial as a "summary  tape." Eberle objected to the admission of Exhibit 26 pursuant  to Rule 1002 and Rule 1006 of the Federal Rules of Evidence.  No objection was made prior to the admission of Exhibit 26  that the edited videotape had not been properly authenticated  or identified pursuant to Rule 901(a).


60
Rule 103(a) precludes an attack on the admission of evidence unless a timely objection is made stating the specific  ground of the objection. See Fed. R. Evid. 103(a). We may,  however, consider a plain error in the absence of an objection  if the erroneous admission of the evidence affected a defendant's substantial rights. See Fed. R. Crim. P. 52(b).


61
The record shows Eberle objected to Officer Helmrick's  testimony that Exhibit 26 depicted Eberle at the Sunday Creek  site pursuant to Rule 901(a). The court sustained the objection  immediately and instructed the jury that they would determine  what was depicted on Exhibit 26. Eberle has failed to demonstrate that the alleged error was prejudicial in that it affected  the outcome of the trial. See United States v. Olano, 507 U.S.  725, 734 (1993).

E. Sufficiency of the evidence

62
McIver and Eberle argue that the evidence presented at trial  was insufficient to establish that they were guilty beyond a reasonable doubt of the offense of conspiring to manufacture  marijuana. There is sufficient evidence to support a conviction if, viewing the evidence in the light most favorable to the  prosecution, any rational trier of fact could have found the  essential elements of the crime beyond a reasonable doubt.  See United States v. Nelson, 137 F.3d 1094, 1103 (9th Cir.  1998).


63
The record contains sufficient evidence to persuade a  rational trier of fact that Eberle conspired with McIver to  manufacture marijuana. In addition to the photograph of  Eberle contained in Exhibit 26, he was in the Toyota 4Runner  when it returned from the Sunday Creek area after the marijuana plants had been harvested. He was also observed carrying a large, bulky garbage bag containing stems or rods.  Marijuana leaves were found in the Toyota 4Runner the next  day.


64
McIver argues that the photographs which depict him  bending over a marijuana plant, taking a photograph of the  marijuana plants, and show his Toyota 4Runner in the parking  area are insufficient to show beyond a reasonable doubt that he conspired to manufacture marijuana in a national forest.  We are persuaded from our review of the record that the circumstantial evidence produced by the Government was sufficient to persuade a rational trier of fact that McIver is guilty  of conspiracy to manufacture marijuana. The Government's  case was not based solely on the photographic exhibits. The  evidence when reviewed as a whole, including the facts that McIver drove to the Sunday Creek area on the same night that  the marijuana plants were harvested, and returned carrying  bulky garbage bags containing stems or rods, satisfies the reasonable doubt standard.


65
F. Propriety of the supplemental jury instruction on the definition of "manufacturing"


66
McIver and Eberle contend that the trial court erred by giving a supplemental jury instruction after the Rule 30 conference and after closing arguments were given. Rule 30  provides that:


67
At the close of the evidence or at such earlier time during the trial as the court reasonably directs, any party may file written requests that the court instruct the jury on the law as set forth in the requests . .. . The court shall inform counsel of its proposed action upon the requests prior to their arguments to the jury.


68
Fed. R. Crim. P. 30.


69
McIver argues that this error "seriously impaired the effectiveness of [his] closing argument." We review a trial court's  decision to give a supplemental jury instruction for an abuse  of discretion. See United States v. Solomon, 825 F.2d 1292,  1295 (9th Cir. 1987). However, where the party fails to object  at trial or fails to state distinctly the grounds for the objection,  we review only for plain error. See United States v. Dorri, 15 F.3d 888, 891 (9th Cir. 1994).


70
On the second day of trial, the court conducted a Rule 30  hearing on jury instructions. After the close of evidence, the  court heard McIver and Eberle's motion for a judgment of  acquittal on Counts I and II. The court granted the motion  with respect to Count II (possession of marijuana with intent  to distribute). As a result, the jury instructions were revised,  with the concurrence of counsel. Neither side proposed an  instruction on the definition of "manufacture, " although the  charge to the jury stated that "the defendants are charged in  the indictment . . . with conspiracy to manufacture  marijuana." During his closing argument, counsel for McIver  made eleven references to the fact that there was no evidence  of "manufacturing" marijuana. During deliberations, three  jurors sent a note to the judge asking, "What is  manufacturing?" The judge conferred with counsel for both  sides and decided to provide the jury with a supplemental  instruction consisting of the definitions of "manufacture" and  "production" contained in the statute under which the defendants were charged. See 21 U.S.C. S 802 (15) & (22). McIver  and Eberle objected on the ground that the instruction would  be "confusing to the jury," and stated that "the jury should be  allowed to determine on their own what they believe`manufacturing' is." The court overruled the objection. The jury was  instructed as follows:


71
The term `manufacture' means the production, preparation, propagation, compounding, or processing of  a drug or other substance, either directly or indirectly or by extraction from substances of natural origin, or independently by means of chemical synthesis, and includes any packaging or repackaging of such sub stance or labeling or relabeling of its container. The term `production' includes the manufacture, planting, cultivation, growing, or harvesting of a con trolled substance.


72
The first sentence is taken verbatim from 21 U.S.C.S 802(15)  and the second from 21 U.S.C. S 802(22).


73
Under the law of this circuit,"[t]he necessity, extent  and character of additional instructions are matters within the  sound discretion of the trial court." United States v. Collom,  614 F.2d 624, 631 (9th Cir. 1979) (citations omitted). However, the district court has an obligation, when a jury requests  clarification on an issue, to "clear away the confusion `with  concrete accuracy.' " United States v. McCall, 592 F.2d 1066,  1068 (9th Cir. 1979) (quoting Bollenbach v. United States,  326 U.S. 607, 612-13 (1946)). By asking "what is  manufacturing?" the jury clearly indicated its confusion on  this issue. The district court correctly decided that the jury  instructions were inadequate without a definition of manufacturing. Rather than "confusing the jury" by giving the instruction, as McIver and Eberle contend, the district court judge  was eliminating confusion, as required by McCall . See id.


74
McIver and Eberle also contend, for the first time on  appeal, that the effectiveness of McIver's closing argument was seriously impaired by the supplemental instruction defining "manufacturing." Specifically, they claim that "[h]ad  counsel known that that instruction was going to be given, he  would not have stressed the use of the word `manufacture' in  closing with the jury." However, because McIver did not specifically state this ground for his objection before the district  court, we review this contention for plain error. See Dorri, 15  F.3d at 891(citing Fed. R. Crim. P. 30). "Plain error" is error  that is clear under existing law and affects a defendant's substantial rights. See Olano, 507 U.S. at 734. The district court  did not commit plain error because the supplemental instruction consisted of a correct statement of law. The court merely  defined a term used in the original charge to the jury, and the  instruction was essential to clear up the jury's confusion.


75
G. Admissibility of evidence suppressed at trial in calculating the Sentencing Guideline range


76
McIver and Eberle challenge the denial of their motion to  exclude from consideration as relevant conduct evidence that  was seized in violation of the Fourth Amendment. We review  de novo a district court's interpretation of the Sentencing  Guidelines. See United States v. Garcia, 135 F.3d 667, 669  (9th Cir. 1998). A court's factual findings are reviewed for  clear error. See United States v. Reed, 80 F.3d 1419, 1421 (9th  Cir. 1996).


77
In opposing McIver and Eberle's motion to exclude the 63  marijuana plants found in their basement from consideration as relevant conduct, the Government contended that under  United States v. Kim, 25 F.3d 1426 (9th Cir. 1994), a district  court must determine the subjective intent of the officers in  seizing evidence in violation of the Fourth Amendment in  deciding whether the evidence can be considered as relevant  conduct for calculation of the Sentencing Guideline range  under United States Sentencing Guidelines S 1B1.3.1 The  prosecutor argued that the facts demonstrated that the officers  were surprised to find the "grow operation" in the McIver/  Eberle basement. He argued further their intent was to seize  the marijuana plants harvested in the Sunday Creek area, and  that the plants in the basement were discovered during a protective sweep of the residence. The prosecutor requested the  court to find that the discovery of the plants in the basement  was "much more by chance than by design."


78
The court denied the motion to exclude the evidence under  the relevant conduct provisions of U.S.S.G. S 1B1.3, but was  unclear as to the basis of its decision.


79
Prior to the adoption of the Sentencing Guidelines, courts  generally allowed illegally seized evidence to be considered  by the sentencing judge. See, e.g., United States v. Lee, 540  F.2d 1205, 1210-1211 (4th Cir. 1976); United States v.  Schipani, 435 F.2d 26, 28 (2d Cir. 1970). In 1968, we created  an exception to the general rule in Verdugo v. United States,  402 F.2d 599 (9th Cir. 1968). We held in Verdugo  that  "where, as here, the use of illegally seized evidence would  provide a substantial incentive for unconstitutional searches  and seizures, that evidence should be disregarded by the sentencing judge." Id. at 613. We reasoned that because at the  time of the illegal search, "the agents already had in their possession sufficient evidence to convict Verdugo of the [earlier]  transaction," id. at 612, allowing the use of the illegally seized  evidence at sentencing would provide the "substantial  incentive" in this case. Specifically, we stated that "[u]nless  the evidence were unavailable for sentence as well as conviction, the agents had nothing to lose by risking an unlawful  search: If the motion to suppress were denied, Verdugo could  be convicted of an additional offense; if it were granted, the  sentence on the original charge could still be enhanced." Id.


80
In Kim, we described the exception created by Verdugo as  an "objective inquiry" into whether, under the circumstances,  the officers had "an undue incentive to act" in violation of the  Fourth Amendment. 25 F.3d at 1435 & n.9. We noted that  other circuits have articulated a more limited "subjective  test." See id. Under this test, illegally seized evidence will be  excluded at sentencing only where the defendant can show  that "officers obtained evidence expressly to enhance a  sentence." United States v. Tejada, 956 F.2d 1256, 1263 (2d  Cir. 1992).


81
In Kim, we held that the Sentencing Guidelines implemented in 1987 require the use of all relevant conduct, including evidence suppressed at trial, for purposes of calculating  the offense level under U.S.S.G. S 1B1.3. See 25 F.3d at  1432-34. We reserved the issue of whether an exception to  this rule still applies, and whether Verdugo's "objective inquiry" or the "subjective" test of other circuits should be  used, because the facts of Kim did not fall within either formulation of the exception. See id. at 1434 n.8, 1435 n.9.


82
A review of the facts of this case demonstrates that the  district court did not clearly err in ruling that the 63 marijuana  plants, which had been suppressed at trial, could be considered for sentencing purposes. McIver and Eberle failed to  demonstrate that the officers "obtained [the ] evidence  expressly to enhance a sentence." Tejada, 956 F.2d at 1263.  They also failed to meet the objective test laid out in Verdugo.  At the time of the illegal search of their residence, McIver and  Eberle had not been indicted or charged with any offense. Cf.  Verdugo, 402 F.2d at 609 (complaint charging Verdugo with  one offense had been filed at time of illegal search). More  importantly, it was not clear at the time of the search that sufficient admissible evidence existed to convict McIver and  Eberle on any drug-related charge. See id. at 612 n.21 ("Quite  different considerations would apply if the object of the  search were to obtain evidence to support a single charge on  which the defendant was later convicted. If the additional evidence was necessary to obtain any conviction at all, the danger of exclusion at trial would afford a substantial deterrent to  an illegal search."). It is true that the officers had photographic evidence that McIver and Eberle were in the vicinity  of the plants. However, they were not depicted watering or  cultivating the plants. Furthermore, the cameras recorded the  images of other individuals near the site. Under these circumstances, law enforcement officers could not be confident that  a jury would conclude that both McIver and Eberle were responsible for tending and harvesting the plants. The district  court did not err in considering the fact that 63 marijuana  plants were found in the basement of the McIver/Eberle residence as relevant conduct in calculating the Sentencing  Guideline range under U.S.S.G. S 1B1.3.


83
AFFIRMED.



Notes:


1
 U.S.S.G. S1B1.3(a) provides in pertinent part as follows:
(a) Chapters Two (Offense Conduct) and Three (Adjustments). Unless otherwise specified, (i) the base offense level where the guideline specifies more than one base offense level, (ii) specific offense characteristics and (iii) cross references in Chapter Two, and (iv) adjustments in Chapter Three, shall be determined on the basis of the following:
(1)(A) all acts and omissions committed, aided, abetted, counseled, commanded, induced, procured, or will fully caused by the defendant; and
(B) in the case of a jointly undertaken criminal activity (a criminal plan, scheme, endeavor, or enterprise undertaken by the defendant in concert with others, whether or not charged as a conspiracy), all reason-  ably foreseeable acts and omissions of others in fur therance of the jointly undertaken criminal activity,
that occurred during the commission of the offense of con viction, in preparation for that offense, or in the course of attempting to avoid detection or responsibility for that offense;
(2) solely with respect to offenses of a character for which S 3D1.2(d) would require grouping of multiple counts, all
acts and omissions described in subdivisions (1) (A) and (1) (B) above that were part of the same course of conduct or common scheme or plan as the offense of conviction;
(3) all harm that resulted from the acts and omissions speci fied in subsections (a) (1) and (a) (2) above, and all harm that was the object of such acts and omissions; and
(4) any other information specified in the applicable guide line.


KLEINFELD, Circuit Judge, concurring:

84
I join in all of the majority opinion except for part II(B).  That section holdsthat installing tracking devices on the chassis of the automobile did not constitute a seizure subject to  Fourth Amendment analysis. I think installing tracking  devices on automobiles and airplanes is subject to Fourth  Amendment analysis as a seizure. Nevertheless error in failing to suppress on this ground was harmless. The evidence  was overwhelming, and McIver was so successfully tracked  visually that the transmissions from the devices attached to  his car were superfluous.


85
The police installed two devices on McIver's car as well as  an antenna under the bumper cover. The officer who installed  one of them testified that installation went "not very well." He  had no prior experience installing this type of equipment. The  wrong kinds of batteries were installed, which "actually  shorted themselves out." The second device was apparently  installed successfully and worked fine.


86
Electronic transmitters are installed by police officers on  cars, airplanes, boats and other vehicles so that they can track  them. The devices emit radio signals. The police use receivers  to pick up the signals and identify where they are coming  from. Some of the devices emit constant or frequent signals,  some occasional signals. They may be combined with global  positioning devices.


87
When a transmitter is installed on or in a vehicle without  the owner's consent there may not be an invasion of any area for which there is a reasonable expectation of privacy, but I  think the law requires us to treat the installation as a seizure  for Fourth Amendment purposes. Property is seized, for purposes of Fourth Amendment analysis, where there is "some  meaningful interference with an individual's possessory  interests."1 The interest to which seizure analysis is addressed  in this case is not a person's liberty to drive on a public street  without a police officer watching, because that liberty is not  protected. Rather, it is the possessory interest of the owner of  a vehicle in excluding individuals from performing mechanical work on his vehicle or altering it without his consent.


88
Fourth Amendment analysis was extended from protection  of property to protection of privacy, to protect privacy from  government intrusion even where the individuals intruded  upon lack any property interest in the area where the intrusion  was made.2 That the Fourth Amendment does protect privacy  even where the protected person has no property, does not  imply that where the person does have a property interest, it  is not protected from seizure in the absence of a privacy interest. The Supreme Court recently so held, unanimously, in  Soldal v. Cook County,3 as we noted in our en banc opinion  in Armendariz v. Penman.4Soldal holds, in the total absence  of any privacy interest, that "the Fourth Amendment protects  property as well as privacy."5 Though the Court had previously, in Cardwell v. Lewis,6 upheld a search in which paint  was scraped from a murder suspect's car, Soldal  notes that in  Cardwell only a four Justice plurality joined in that view,  there was probable cause at the time to seize the car, and  "both the plurality and dissenting Justices considered the defendant's auto deserving of Fourth Amendment protection  even though privacy interests were not at stake."7


89
Thus under Soldal, despite McIver's lack of a privacy interest in the chassis of his car, he had a right guaranteed by the  Fourth Amendment to be free of a "seizure" of his car unless  a search warrantissued upon probable cause or there was a  special exigency. Though exigency that avoids the need for a  warrant easily arises in automobile search and seizure cases,  no finding of exigency has been made, nor has exigency been  urged, as a reason to dispense with a search warrant in this  case.


90
Whether installing a transmitter on or in a vehicle is a  "seizure" for Fourth Amendment purposes depends on  whether the installation involves "some meaningful interference with an individual's possessory interests."8 "One of the  main rights attaching to property is the right to exclude others."9  Owners of vehicles assiduously exclude others from touching  or altering the mechanical parts of their vehicles without consent.


91
American cities are cacophonous with the noise of car  alarms, because people arrange to be alerted if anyone touches  their cars. They do not like strangers touching their cars. Nor  is their concern necessarily misplaced. A police officer not  trained as a mechanic might unwittingly damage an automobile in the course of installing a transmitter. In the case at bar,  the police officer who installed one of the devices testified that because of an error regarding batteries, the batteries some  time after installation "shorted themselves out. " Shorts emit  heat, a serious safety concern near a gasoline tank.


92
Now that automobile operation depends heavily on electronic signals between components and computers, owners  would naturally be concerned lest radio transmitters and magnets might affect safety and proper operation of the vehicles.  Cosmetic damage from scratches as the devices are installed  and removed and adhesives might affect resale value. With  airplanes and boats, the safety concerns of owners are likely  to be magnified. Anyone who boards an airplane is told to  turn off all Walkmans, CD players, and other devices upon  takeoff and landing because they may emit radio signals that  would interfere with safe operation of the airplane. An owner  of a boat or airplane would reasonably be concerned that a  police transmitter would do the same thing for the same reason, jeopardizing his and his passengers' safety. An airplane  owner would also be deeply concerned about the safety risk  if anyone but a certified aircraft mechanic did anything to his  plane.


93
This is not to say that police officers may not attach transmitters to automobiles. The point of the discussion above is  that the owner of a vehicle has a possessory interest that is  meaningfully interfered with if a transmitter is installed, even  where the installation does not interfere with a reasonable  expectation of privacy. That is to say, installing a beeper is a  seizure. Many seizures by law enforcement officers are per- missible under the Fourth Amendment. Fourth Amendment  law is especially tolerant of seizures of vehicles, because they  are so easily moved. But it is one thing to justify a seizure,  and quite another not to treat substantial interference with  possessory interests as a seizure.


94
In this case, no warrant was obtained to allow the seizure,  and no exception such as exigency was urged to avoid the  need for a warrant. All that the government has argued is that  the transmitter was installed when the car was outside the curtilege, an argument that disregards the owner's possessory  interest in his car, as opposed to his privacy interest in his curtilege. Surprisingly, I have not found much definitive law on this  issue. The Supreme Court has spoken on the related issues  discussed above, but not on whether installation of a transmitter on or in a vehicle is a seizure for purposes of Fourth  Amendment analysis. Three Justices have noted that certiorari  might be desirable on "the legality of a warrantless installation of a beeper."10 We have carefully distinguished in our circuit's "beeper" cases between the Fourth Amendment  interests at stake in monitoring the signals, and those at stake  in installation of the devices, and have not reached the question whether installation without consent is a seizure.11 Other  circuits are in some disarray, and most or all of the beeper  decisions focus exclusively on privacy, having come down  before Soldal made it clear that property interests needed to  be considered even if privacy interests were negligible.12


95
Much of the disarray in the law arises from confusion of  the privacy interests and the property interests protected by  the Fourth Amendment. Although transmitters reduce the privacy of the people who travel without knowing that they are  carrying transmitters, the law is clear that this privacy interest  is not protected under the Fourth Amendment, where the  travel is public.13 If the owner of a car consents to installation  of a transmitter in his car, this consensual alteration would  probably not turn into a "seizure" for Fourth Amendment purposes if the car were transferred to another.14 United States v.  Karo,15 upon which the majority relies, does not involve nonconsensual installation of a transmitter on an automobile, as  the case at bar does. In Karo, the DEA agents, authorized by  a court order, installed a transmitter in a can of ether that the  government owned at the time, then had their cooperating  individual sell the can of ether to the cocaine dealers who  would unknowingly transmit their location when they moved  the can. The Court held that this did not interfere meaningfully with the cocaine dealers' possessory interests in the can.16  Karo is analogous to the owner consenting to installation of  a beeper on his car, and then selling it with the beeper  installed to another.


96
Law enforcement needs regarding beepers can be adequately served by search warrant procedures, and the broad  exceptions to search warrant procedures for easily moveable  vehicles. Those are not the only interests deserving of protection. People care about their cars, planes and boats, and often  object vehemently to any unconsented to mechanical work or even touching of these valuable effects. That concern is protected by the law of property and by the Fourth Amendment  right to be free from unreasonable seizures. In the absence of  a warrant issued by a neutral magistrate, or applicability of an  exception to the Fourth Amendment warrant requirement,  people are entitled to keep police officers' hands and tools off  their vehicles.



Notes:


1
 United States v. Karo, 468 U.S. 705, 712 (1984).


2
 Katz v. United States, 389 U.S. 347 (1967).


3
 Soldal v. Cook County, 506 U.S. 56 (1992).


4
 Armendariz v. Penman, 75 F.3d 1311, 1320 (9th Cir. 1996) (en banc).


5
 Soldal, 506 U.S. at 62.


6
 Cardwell v. Lewis, 417 U.S. 583 (1974).


7
 Soldal, 506 U.S. at 65.


8
 Karo, 468 U.S. at 712.


9
 Rakas v. Illinois, 439 U.S. 128, 143 n.12 (1978).


10
 Michael v. United States, 454 U.S. 950 (1981) (dissent from denial of  petition for certiorari).


11
 United States v. Brock, 667 F.2d 1311, 1318-22 (9th Cir. 1982);  United States v. Miroyan, 577 F.2d 489, 492 (9th Cir. 1978).


12
 See United States v. Michael , 645 F.2d 252 (5th Cir. 1981) (en banc); United States v. Bailey, 628 F.2d 938 (6th Cir. 1980); United States v.  Moore, 562 F.2d 106 (1st Cir. 1977); United States v. Holmes, 537 F.2d  227 (5th Cir. 1976) (en banc).


13
 United States v. Knotts, 460 U.S. 276 (1983).


14
 United States v. Karo, 468 U.S. 705, 712 (1984).


15
 Id.


16
 Id. at 712-13.


