208 F.3d 626 (7th Cir. 2000)
UNITED STATES OF AMERICA,    Plaintiff-Appellee,v.CLARENCE RICHARDSON, JR.,    Defendant-Appellant.
No. 99-1190
In the  United States Court of Appeals  For the Seventh Circuit
Argued September 24, 1999Decided April 3, 2000

Appeal from the United States District Court  for the Eastern District of Wisconsin.  No. 98-CR-92--Rudolph T. Randa, Judge.
Before BAUER, RIPPLE, and DIANE P. WOOD, Circuit  Judges.
Diane P. Wood, Circuit Judge.


1
Clarence  Richardson, a convicted felon, was charged with  unlawfully possessing a firearm, 18 U.S.C. sec.  922(g)(1), and possessing with intent to  distribute cocaine, 21 U.S.C. sec. 841(a)(1).  Because both the drugs and the gun were found  during a warrantless search of Richardson's home,  Richardson filed a pretrial motion to suppress  the incriminating evidence, which the district  court denied. After a bench trial, Richardson was  convicted on both counts and received a sentence  of 262 months in prison and a $500 fine. In his  appeal, Richardson challenges both the  suppression ruling and the sufficiency of the  evidence to support his conviction. While we find  no reversible error on either aspect of the case,  the more serious issues arise in conjunction with  the search, for the reasons we explain below. In  the final analysis, however, we conclude that the  judgment against Richardson must be affirmed.


2
* On May 9, 1998, the Milwaukee police received a  911 call reporting that a 19-year-old African-  American man named "Lucky" had raped and murdered  a female. The caller said that the victim could  be found in the basement at 1704 N. 37th Street,  a residence the caller described as "a drug  house." The caller identified himself to the 911  operator as "Anthony Carter" and explained that  he lived at the same address. The police had  received a 911 call reporting a murder at the  same address one week before Anthony Carter's  call. That call turned out to be a false alarm:  there was no murder victim.


3
Upon receiving the May 9 call, Milwaukee police  went to 1704 N. 37th Street. The building was a  duplex with upper and lower units; the lower unit  was number 1704. Standing in front of the  building was an African-American male holding a  dog on a chain. The man identified himself to the  police as Clarence Richardson and said he resided  at 1704 N. 37th Street. The police officers  explained to Richardson that they had received a  911 call reporting a murder. Richardson told the  officers that this was the second time that week  that this had happened.


4
Richardson went to take his dog inside the  residence. The police officers instructed him to  secure the dog on the porch, because they needed  to search the residence. Although the police at  one point contended otherwise, the magistrate  judge found that Richardson did not consent to  the search, and this finding was not challenged  further. Before the officers entered the duplex,  they directed anyone else inside to come out.  That call prompted Shannon Purnell, another  African-American male, to come outside. The  officers then entered the lower unit of the  duplex and conducted a search of the entire  house. They did not have a warrant.


5
In the first floor unit the officers observed  drugs (marijuana and crack cocaine) and drug-  packaging materials on the dining room table. In  the southern part of the basement, they saw more  marijuana, two scales of the type commonly used  to weigh drugs, and over 200 baggies. One officer  spotted a Mossberg pistol grip shotgun on the bed  in the front bedroom. Also on the bed were  envelopes addressed to Clarence Richardson and  prescription medications with his name and the  1704 N. 37th Street address on the labels. The  officers did not find a female murder victim.


6
Purnell, who knew Richardson as "C," testified  at Richardson's trial. He said that Richardson  lived in the lower unit of the duplex and slept  in the front bedroom. Purnell explained that he  had been to Richardson's residence six or seven  times and that he had seen Richardson smoking  rock cocaine. Purnell also described seeing  cocaine in Richardson's bedroom, but he did not  know about the marijuana in the basement.  Finally, Purnell testified that one week before  the search, Richardson had told him he purchased  a "pretty pump" (12 gauge shotgun) for between  $150 and $250.


7
A DEA Special Agent testified that the amount  of cocaine, the packaging materials, and the  scale were all consistent with drug dealing, and  an ATF agent testified that an investigation of  the shotgun's ownership revealed that one Lucky  Allen was the owner. When the ATF agent had asked  Allen about the gun, Allen told him that he owned  the gun but that he no longer possessed it  because it had been stolen.


8
Richardson filed a motion to suppress the  evidence gathered during the warrantless search  of his home. Magistrate Judge Goodstein  recommended that Richardson's motion be denied,  and Richardson filed objections to that report.  In light of the objections, the district court  decided in an order issued on August 31, 1998, to  remand the motion to the magistrate judge for an  evidentiary hearing. After the hearing, the  magistrate judge issued a second recommendation  to deny the motion to suppress, finding first  that Richardson had a privacy interest in the  residence and second that exigent circumstances  justified the warrantless entry. Richardson again  objected. At that juncture, in an order dated  September 22, 1998, the district court adopted  the magistrate judge's recommendation and denied  Richardson's motion.


9
After the motion was denied, Richardson  testified. He said he was the landlord and  caretaker of 1704 N. 37th Street as well as  several other properties in the area. During the  two weeks before the search, he was staying at  another Milwaukee address, but he continued to  keep his clothes and medication and to receive  mail at 1704 N. 37th Street. Sometime in April  1998, he permitted Lucky Allen to move into the  1704 N. 37th Street residence as a favor to some  family members. After catching Allen with a  shotgun, Richardson gave him two weeks' notice to  vacate. Allen persuaded Richardson to let him  stay by assuring him that he would not keep the  gun. Richardson testified that he never saw drugs  at 1704 N. 37th Street. The district court found  that this added up to at least constructive  possession of the gun and drugs, and hence  criminal liability for Richardson under sec.  922(g)(1) and sec. 841(a)(1).

II

10
A.  Denial of Richardson's Motion to Suppress


11
In reviewing a district court's denial of a  motion to suppress, we review findings of  historical fact and credibility determinations  for clear error. United States v. Johnson, 170  F.3d 708, 713 (7th Cir. 1999). We give de novo  review to mixed questions of law and fact such as  determinations of probable cause or reasonable  suspicion. Id., citing Ornelas v. United States,  517 U.S. 690, 699 (1996). Whether or not exigent  circumstances were present is also a mixed  question of law and fact, see United States v.  Howard, 961 F.2d 1265, 1267 (7th Cir. 1992), and  thus we also review that question de novo.


12
"A warrantless search or seizure is 'per se  unreasonable unless the police can show that it  falls in one of a carefully defined set of  exceptions based on the presence of "exigent circumstances."'"  United States v. Bennett, 908 F.2d 189, 192 (7th  Cir. 1990), quoting Coolidge v. New Hampshire,  403 U.S. 443, 474-75 (1981). "[T]he Fourth  Amendment does not bar police officers from  making warrantless entries and searches when they  reasonably believe a person within is in need of  immediate aid. Similarly when the police come  upon the scene of a homicide they may make a  prompt warrantless search of the area to see if  there are other victims or if a killer is still  on the premises." Mincey v. Arizona, 437 U.S.  385, 392 (1978). Nevertheless, there is no  general exception from the Fourth Amendment for  searches of homicide scenes. Id. at 393-94, 98 S.Ct.2408.


13
This court has found that exigent circumstances  justified a warrantless search where the police  reasonably feared for the safety of someone  inside the premises. United States v. Brown, 64  F.3d 1083, 1086 (7th Cir. 1995); United States v.  Arch, 7 F.3d 1300, 1303-05 (7th Cir. 1993);  United States v. Salava, 978 F.2d 320, 324-25  (7th Cir. 1992). However, a police officer's  subjective belief that exigent circumstances  exist is insufficient to make a warrantless  search. Instead, as is normally the case for  Fourth Amendment inquiries, the test is  objective: "the government must establish that  the circumstances as they appeared at the moment  of entry would lead a reasonable, experienced law  enforcement officer to believe that someone  inside the house, apartment, or hotel room  required immediate assistance." Arch, 7 F.3d at  1304.


14
We find this a very close case. The police  officers' claim of exigent circumstances was  based entirely on the 911 call, and the 911  operators had received a bogus call with almost  exactly the same report only a week earlier.  Pointing out the risk of fraud or, at the very  least, unreliable and unproven information from  911 callers, Richardson argues that a 911 call  cannot by itself justify a warrantless search or  furnish a reasonable basis for an officer to  believe that someone inside the residence needs  assistance. This line of argument goes too far,  however; it invites us to adopt a presumption  under which a 911 call could never support a  finding of exigent circumstances. Many 911 calls  are inspired by true emergencies that require an  immediate response. Those factors have led both  this court and others to conclude that 911 calls  reporting an emergency can be enough to support  warrantless searches under the exigent  circumstances exception, particularly where, as  here, the caller identified himself. See, e.g.,  United States v. Cunningham, 133 F.3d 1070, 1072-  73 (8th Cir.), cert. denied 523 U.S. 1131 (1998);  Salava, 978 F.2d at 321, 324-25. A 911 call is  one of the most common--and universally  recognized--means through which police and other  emergency personnel learn that there is someone  in a dangerous situation who urgently needs help.  This fits neatly with a central purpose of the  exigent circumstances (or emergency) exception to  the warrant requirement, namely, to ensure that  the police or other government agents are able to  assist persons in danger or otherwise in need of  assistance. See United States v. Moss, 963 F.2d  673, 678 (4th Cir. 1992); Wayne v. United States,  318 F.2d 205, 212 (D.C. Cir. 1963) (Burger, J.)  ("The need to protect or preserve life or avoid  serious injury is justification for what would be  otherwise illegal absent an exigency or  emergency."). The efficient and effective use of  the emergency response networks requires that the  police (and other rescue agents) be able to  respond to such calls quickly and without  unnecessary second-guessing. As then-Circuit  Judge Burger stated in Wayne, "[T]he business of  policemen and firemen is to act, not to speculate  or meditate on whether the report is correct.  People could well die in emergencies if police  tried to act with the calm deliberation  associated with the judicial process." 318 F.2d  at 212.


15
Taking a more subjective tack, Richardson next  argues that the police officers' behavior reveals  that they did not believe that exigent  circumstances existed. He points out that the  police parked half a block away; they did not ask  Richardson to unlock the basement door; they  chose to enter through the main door to the unit  rather than the basement's separate entrance;  they searched the bedroom and other areas before  proceeding to the basement (where the victim was  reportedly located); and they did not ask for  directions on the fastest route to the basement.  Richardson also points out that the police did  not summon an ambulance, even though they  justified their warrantless entry on the  possibility that the victim might still be alive.  Coupled with the earlier crank call, these  undisputed facts show in Richardson's opinion  that the police did not regard the situation as  a bona fide emergency.


16
This line of argument cannot save the day for  Richardson, however, to the extent that it is  based on the subjective state of mind of the  officers. If Richardson is inviting us to modify  the existing test for exigent circumstances to  add these subjective elements, we respectfully  decline. Creating a subjective standard would be  a double-edged sword: while it might protect some  people from warrantless searches in those few  instances where the police do not really believe  an injured person is in need of assistance, it  would also open up the possibility of warrantless  searches anytime that police officers actually  believed that an exigency existed--regardless of  the objective basis of that belief. We adhere to  our well-established rule that such a subjective  belief cannot justify a warrantless entry. E.g.,  Arch, 7 F.3d at 1304. Using an objective standard  ensures that there is some control on the  reasonableness of police officers' behavior. This  kind of external accountability is especially  important when warrantless searches of homes are  at stake.


17
Richardson also appears to suggest, however,  that on the facts of this case it was objectively  unreasonable for the police to search the house.  The 911 caller did not indicate that a rape or  murder was in progress; the caller said instead  that the crime was complete. Faced with a report  that there is a corpse in a house, it is hard to  see why it is objectively reasonable to search in  the hopes of finding a person who is still alive,  but perhaps seriously wounded. Concern about  whether exigent circumstances could be found on  this kind of record was what prompted the  district court to order an evidentiary hearing on  precisely this issue. At that hearing, the police  officers testified that in their experience,  laypersons without medical knowledge are not in  a position to determine whether a person is dead  or alive. Someone who appeared to be dead might  revive with immediate medical treatment. The  officers stated, therefore, that they assume that  anyone reported dead might be alive unless the  report comes from qualified personnel such as a  paramedic unit. It was on the basis of this  assumption that they entered the house. Last, the  officers testified that they did not personally  know about the earlier bogus report.


18
Like the magistrate judge and the district  court before us (whose conclusions we are  reviewing de novo), we agree that it was  objectively reasonable for the officers to  conclude that the situation presented exigent  circumstances on these particular facts. This is  not a case where the report indicated that the  body had been languishing in the house for  several days. Nor is it a case where other  evidence might have made it clear that the victim  was indeed dead, and not hovering on the verge of  death. A modus operandi that is designed to save  potential fatalities, where it is objectively  reasonable to think that this is possible, is  permissible. We note in this connection that  Richardson did not introduce any evidence to  rebut the officers' assertion that this was their  practice, nor did he challenge their empirical  assumption that lay witnesses were often wrong in  their assumption that someone was beyond rescue.


19
Last, Richardson argues that to find exigent  circumstances on these facts would lead to abuse  of the 911 system: people with a grudge would  have an incentive to make phony calls about their  neighbors in order to allow the police to enter  and search their neighbors' property without a  warrant. Or perhaps competing drug dealers would  report murders on one another's property so the  premises would be searched and the competitor put  out of business. The district court's first order  on the motion echoes a similar concern: "The rule  . . . would allow police a free and immediate  warrantless entry into a dwelling upon every  report of a murder, with no regard to its  details." While we do not exclude the possibility  of a case in which it would be objectively  unreasonable for a police officer to rely on a  911 call, because of additional information  available to the officer, this is not that case.  It may even be possible, in those rare cases  where a false emergency call is made, that the  "victim" (that is, the person whose house is  searched) might have a remedy against the caller.  Whether or not this is true, we have no evidence  indicating that the 911 system is abused so often  that it is objectively unreasonable for the  police to rely on a call like the one Carter made  here. We therefore agree that the district court  correctly denied Richardson's suppression motion  because the warrantless search fell within the  exigent circumstances exception to the warrant  requirement.

B.  Insufficiency of the Evidence

20
We review questions of sufficiency of the  evidence "in the light most favorable to the  government and ask whether any rational trier of  fact could find the essential elements of the  crime beyond a reasonable doubt." United States  v. Rogers, 89 F.3d 1326, 1334 (7th Cir. 1996);  see also United States v. Griffin, 150 F.3d 778,  784 (7th Cir. 1998).


21
The only element of the two crimes that  Richardson argues the government failed to prove  was whether he had any dominion or control over  either the gun or the drugs. Both offenses  require "knowing possession" of either a gun or  controlled substances. In addition to actual  possession, possession can be constructive, and  constructive possession can be established  through circumstantial evidence. United States v.  Gill, 58 F.3d 334, 336 (7th Cir. 1995).  Constructive possession exists where the evidence  demonstrates ownership, dominion, authority, or  control. Id.; United States v. Hernandez, 13 F.3d  248, 252 (7th Cir. 1994). Constructive possession  may be sole or joint. See United States v.  Kitchen, 57 F.3d 516, 521 (7th Cir. 1995); United  States v. Salazar, 983 F.2d 778, 782 (7th Cir.  1993). Establishing constructive possession  requires that the government establish a nexus  between the accused and the contraband, in order  to distinguish the accused from a mere bystander.  United States v. Windom, 19 F.3d 1190, 1199 (7th  Cir. 1994).


22
The government's theory was that Richardson's  constructive possession of the narcotics and the  gun stemmed from his connection to the residence.  It is disputed whether Richardson lived at 1704  N. 37th Street. (Purnell testified Richardson  lived and slept there; Richardson testified he  was living elsewhere and told the officers he was  the "caretaker" of 1704 N. 37th Street.) But  regardless of who is right, it is apparent that  Richardson had a substantial connection to the  house: in his bedroom were multiple medicine  bottles labeled with his name as well as his  clothes; he received his mail at 1704 N. 37th  Street; and he admitted that he was the caretaker  and landlord of the address. This is enough to  prove that Richardson had control over the  property and to establish a nexus between the  contraband and Richardson. Compare Kitchen, 57  F.3d at 519-21 (establishing constructive  possession over firearms where papers and notes  bearing the defendant's name and a bracelet with  the defendant's nickname were found in the same  room of defendant's girlfriend's home as the  guns), with Windom, 19 F.3d at 1200-01 (finding  constructive possession not established where the  only connection between the defendant and the  contraband was their simultaneous presence in the  same house).


23
Richardson does not contest the legal force of  these points. Instead, he alleges that Purnell  perjured himself and that without Purnell's  (perjured) testimony, there would be insufficient  evidence to link Richardson to the house.  Richardson's argument, however, cannot carry the  day. We accord great deference to the trier of  fact regarding credibility determinations.  Nothing in the record suggests that Richardson's  testimony is more reliable than Purnell's.  Because the testimony could have supported either  conclusion, the district court could not have  clearly erred when it chose to believe Purnell  rather than Richardson. See United States v.  Yusuff, 96 F.3d 982, 989 (7th Cir. 1996). In  addition, even without Purnell's testimony, there  was ample evidence linking Richardson to the  drugs and the gun. Richardson was the caretaker  of the residence and exercised control over the  property. On the evening of the search,  Richardson was present. The officers found the  gun in Richardson's bedroom along with his  personal items. Without any help from Purnell,  this evidence establishes Richardson's  constructive possession over the shotgun. The  same can be said for the drugs: they were in  plain view in the main rooms of the house.

III

24
For these reasons, we therefore AFFIRM the judgment of the district court.

