232 F.3d 600 (7th Cir. 2000)
KENNETH H. GOODWIN, JR.  and JACQUELINE GOODWIN, Plaintiffs-Appellees,v.MTD PRODUCTS, INCORPORATED, Defendant-Appellant.
No. 00-1459
In the  United States Court of Appeals  For the Seventh Circuit
Argued September 12, 2000Decided November  14, 2000

Appeal from the United States District Court  for the Western District of Wisconsin  No. 99 C 220--John C. Shabaz, Chief Judge.[Copyrighted Material Omitted]
Before POSNER, COFFEY, and MANION, Circuit  Judges.
COFFEY, Circuit Judge.


1
On June 6, 1998,  Kenneth Goodwin suffered an injury to his  left eye after being struck by a plastic  wing nut discharged from the lawn mower  he was using. Based on his injuries,  Goodwin filed a product liability suit  against MTD Products (the manufacturer of  the lawnmower), claiming that: 1) MTD  negligently manufactured the mower; 2)  the mower left MTD's "possession and  control" in a defective condition; 3) the  mower was unreasonably dangerous; and 4)  MTD breached expressed and implied  warranties relating to the mower. After  trial, the jury awarded Goodwin  $603,167.96 plus costs, and the judge  denied MTD's motions for judgment as a  matter of law and for a new trial. We  affirm.

I.  BACKGROUND

2
In late April 1998, Goodwin purchased an  MTD lawn mower from Wal-Mart and  transported it to his home. According to  Goodwin's testimony, he took it out of the truck and laid it by  the front, by the front porch and [he]  opened the box and took the lawn mower  out and the directions and [he] just kind  of flipped through the directions and  glanced at a few things and . . . then he  flipped the handle up and tightened the  wing nuts on the handle and put some oil  and some gasoline in it and started  mowing [his] lawn.


3
After having used the mower on three or  four prior occasions, Goodwin took the  mower from his garage on June 6, 1998, at  approximately 10:00 in the morning. After  mowing for about 20 minutes, and while  walking directly behind the mower and  approximately five feet from his house,  Goodwin "felt something hit [him] in the  [left] eye and [he] just let go of the  lawn mower and [ ] put [his] hand up to  [his] face and . . . [he] could tell that  [he] was bleeding."1 Goodwin's wife  immediately drove him to the emergency  room at Vernon County Hospital in Vernon,  Wisconsin, and he was transferred to  Gunderson Lutheran Hospital in La Crosse,  Wisconsin, the next day for eye surgery.


4
A few days after his surgery, Goodwin,  while searching his yard in an attempt to  discover what possibly could have hit him  in the eye, discovered a plastic wing nut  in approximately the same area of the  yard where his injury occurred.  Subsequently, Goodwin filed suit alleging  that the lawn mower was dangerous and  defective in that the plastic wing nut  became loose and fell into the mower's  blade due to the vibrations caused by the  lawn mower's motor. According to  Goodwin's theory, the wing nut was then  propelled out the side chute (facing  down) at a high rate of speed  (approximately 190 miles per hour), hit  the ground, bounced off the ground, hit  the house approximately five feet away,  and ricocheted into his left eye. On the  other hand, MTD claimed that the lawn  mower was properly designed and safe, and  that it would have been impossible for  the plaintiffs' "ricochet" theory to have  occurred.


5
However, Goodwin gave the only eye-  witness testimony regarding the accident  and subsequent injury to his left eye.  Furthermore, Goodwin introduced the  deposition of the doctor who performed  his eye surgery as well as expert  testimony as to the manufacture, design,  and condition of the lawn mower. MTD  attempted to counter Goodwin's theory  with expert testimony of its own  concerning the manufacture, design, and  operation of the MTD lawn mower.

A.  The Plaintiffs' Experts
1.  Dr. Christopher Born

6
As the trial judge informed the jury,  "Dr. Christopher Born is a medical doctor  certified in ophthalmology, having  practiced for 20 years at the Gunderson  Lutheran Medical Center in La Crosse,  Wisconsin. He specialized in eye surgery  with a subspeciality in the cornea and  the front part of the eye."


7
According to Dr. Born's deposition  testimony introduced at trial


8
I saw Kenneth Goodwin on the 7th of June,  1998 in the emergency room at Gunderson  Lutheran Hospital with an injury to his  left eye. He had a laceration on the left  lower lid. He had a very unusual  laceration to the left cornea.


9
The cornea is the front window of the  eye and most lacerations of the cornea  caused by flying objects are more a  direct penetration to the cornea. This  one [Goodwin's eye injury] started at one  side of the cornea and sliced and shelved  completely across the cornea ending up  just before it entered the eye. The  reason that type of injury is unusual is  because normal objects are either sharp  enough to penetrate directly into the eye  or large enough that they cause a  concussive injury to the eye. This one  [the injury to Goodwin's eye] was  obviously caused by an object that was  large enough to carry significant  momentum and yet wasn't particularly  sharp.


10
It is my opinion that the broken wing  nut [in this case] is a type of  projectile consistent with the injury to  Mr. Goodwin's cornea. It satisfies that  criteria, being large enough to cause a  significant blow to the eye and  relatively sharp being cut by the lawn  mower to cause the slice and injury to  the eye.


11
After plaintiffs' attorney finished with  the narrative reading of Dr. Born's  deposition testimony, the  defendantelected not to offer a  responsive narrative nor did MTD offer  any expert medical opinion of its own.  Thereafter, the plaintiffs called their  engineering expert, Donald Marty.

2.  Donald Marty
As the district court informed the  jury,2

12
Donald Marty is a licensed professional  engineer with a bachelor's degree in  mechanical engineering and a master's  degree in mechanical engineering from the  University of Wisconsin-Madison.


13
He has been employed by Safety  Engineering Associates in Madison since  1988 and holds various memberships and  certifications. He has lectured and  attended many continuing education  courses.


14
Before reaching any opinion, Marty: 1)  inspected the "subject rope guide and  wing nut from the accident lawn mower";  2) compared the rope guide and wing nut  design used by MTD with other lawn mower  designs; 3) reviewed the operator's  manual; 4) reviewed the safety standards  published by the American National  Standards Institute (ANSI) for lawn  mowers; 5) reviewed the sales literature  from MTD and Wal-Mart; and 6) reviewed  the depositions of the Goodwin's, Dr.  Born, and MTD's expert, Gunter Plamper.  Based on his review of the evidence and  testing he performed to determine the  residual torque of different types of  wing nuts as fastening devices for  different rope guides, Marty concluded  that MTD's use of a plastic wing nut in  the assembly of the lawn mower's rope  guide was unreasonably dangerous.


15
Question: Do you have an opinion to a  reasonable degree of engineering  certainty as to whether or not the lawn  mower, specifically the plastic wing nut  in question, was defective and  unreasonably dangerous as sent by the manufacturer [MTD] and purchased by the  consumer [Goodwin]?


16
Answer: Yes. In my opinion it is defective  and unreasonably dangerous.


17
Questions: Why is that?


18
Answer: Because the plastic wing nut does  not have a locking feature and it can  easily unthread if it should loosen.


19
Question: Is it feasible using the exact  design of this mower to use a lock nut  with a plastic or nylon insert?


20
Answer: Yes it is. . . . That would be the  lock nut and rope guide that I talked  about earlier from the Weed Eater lawn  mower. That design has two features. One,  it has a shoulder formed onto the rope  guide so it can be tightly clamped to the  handle.


21
In addition it has the steel lock nut  with a nylon insert which one can tightly  clamp the rope guide to the handle of the  lawn mower and also it has the locking  feature that we've been talking about. If  the nut should be loose for whatever  reason, it will not unthread as long as  the nylon locking feature is engaging the  threads. In my opinion that's a much  safer design.


22
Additionally, Marty testified that the  plastic wing nut turned "very, very  easily" and demonstrated this by turning  the plastic wing nut with his finger.


23
On cross-examination, Marty made it  clear that his testimony was focused  toward the defective nature of the  plastic wing nut used on the MTD lawn  mower and stated, "I have not reviewed or  analyzed other parts of the lawn mower.  They may or may not be defective, but I  do not have opinions." Furthermore, Marty  admitted that the lawn mower complied  with ANSI standards. Additionally, Marty  consistently maintained, throughout both  direct and cross-examination, that the  use of a plastic wing nut was "defective  and unreasonably dangerous" because "the  plastic wing nut does not have a locking  feature and it can easily unthread if it  should loosen" due to the vibrations of  the mower's motor, and that lawn mowers  should be equipped with steel lock nuts  with nylon threads because it is "a much  safer design."

B.  The Defendant's Expert Gunter  Plamper

24
After MTD's motion for a directed  verdict was denied, the defense called  Gunter Plamper, an engineer, as its  rebuttal expert. Plamper is a registered  professional engineer in Germany and  worked as an engineer in Nuremberg,  Germany, for Siemans Company before  coming to the United States in 1964.  Plamper was initially hired by MTD in  1964 as a project engineer and given the  task of designing a high-end self-  propelled walk-behind lawn mower. In  1970, he was promoted to chief engineer  of consumer products, and remained in  that position until 1994. Currently, he  is MTD's vice president in charge of  product development and safety.  Furthermore, Plamper holds eight patents  which have been incorporated into mass-  produced products. Additionally, he is  involved with ANSI and is a member of the  Engineering Subcommittee for the Outdoor  Power Equipment Institute as well as a  number of other safety organizations.


25
As one would expect, Plamper had a much  different opinion as to the safety of the  MTD lawn mower in question.


26
Question: Mr. Plamper, in your opinion  based on a reasonable degree of  engineering certainty is this model mower  safe to use?


27
Answer: Yes.


28
Question: How so?


29
Answer: It meets all the requirement[s].  The warnings make the operator aware of  the danger of a thrown object. I mean he  would behave accordingly [sic] to the  warning and the instructions this  accident would not have occurred.


30
Question: Can the mower be operated safely  without an injury to the operator?


31
Answer: Yes. There are millions of them  used every day and very safe [sic].


32
Question: Do you have an opinion, Mr.  Plamper, based on a reasonable degree of  engineering certainty as to the condition  of the machine at the time of design and  manufacture when it left MTD?


33
Answer: Yes.


34
Question: And what is your opinion?


35
Answer: My opinion is when this machine  left MTD it met all the requirements and  was perfectly safe for consumer use.


36
Question: When it left MTD did it have any  defects?


37
Answer: It did not have any defects in  manufacturing or design.


38
*  *  *


39
Question: Mr. Plamper, do you have an  opinion based on a reasonable degree of  engineering certainty as to whether or  nor it is safe to use this wing nut on  this mower with this rope guide?


40
Answer: Yes, I have an opinion.


41
Question: And what is your opinion?


42
Answer: My opinion is that it's very safe  to use this kind of an application on the  mower without any problems.


43
Question: It's been said in court [by  Marty] that the wing nut is subject to  vibrating off. Do you agree?


44
Answer: Well, the vibration on the handle,  yes, but this wing nut will not come off  when you tighten it. . . .


45
*  *  *


46
Question: Mr. Plamper, based on your  knowledge, your experience, your  training, and your testing do you have an  opinion based on a reasonable degree of  engineering certainty as to whether Mr.  Goodwin could have been hit with a wing  nut while operating the lawn mower in the  operator zone [behind the lawn mower]  with the [discharge] chute down?


47
Answer: That it is impossible, including a  ricochet.


48
Plamper, in over 35 pages of direct  testimony, gave numerous examples of why  he was of the opinion that the lawn mower  was safe and how it complied with all  applicable safety standards. Plamper also  testified as to the results of the tests  he had performed on the same model lawn  mower and that his testing confirmed his  opinion that the lawn mower was safe.  However, the district court refused to  allow Plamper to testify as to the  impossibility of a wing nut causing  Goodwin's eye injury on the grounds that  Plamper was not qualified as a medical  expert to testify on the issue.  Furthermore, the trial judge excluded, as  cumulative, a videotape that MTD wanted  to introduce showing Plamper conducting  some of the tests that he discussed as  well as a videotape of the same model  lawn mower being assembled.


49
Based on the evidence adduced at trial,  the jury returned a verdict in favor of  Goodwin, finding that MTD was 65%  responsible for the accident and that  Goodwin was 35% responsible for the  accident. As mentioned previously,  Goodwin was awarded $603,167.96 plus  costs. MTD appeals.

II.  ISSUES

50
On appeal, MTD argues that the trail  judge erroneously: 1) denied its motions  for judgment as a matter of law and for  a new trial because, according to MTD,  the evidence Goodwin presented at trial  was insufficient to permit a reasonable  jury to find in his favor; and 2)  excluded expert testimony.

III.  DISCUSSION
A.  Standard of Review

51
While we review the denial of a motion  for judgment as a matter of law de novo,  Emmel v. Coca-Cola Bottling Co. of Chicago, 95 F.3d 627, 629 (7th Cir.  1996), this court's inquiry is limited to  "whether the evidence presented, combined  with all reasonable inferences  permissibly drawn therefrom, is  sufficient to support the verdict when  viewed in the light most favorable to the  party against whom the motion is  directed." McNabola v. CTA, 10 F.3d 501,  515 (7th Cir. 1993). "In other words, we  are limited to assessing whether no  rational jury could have found for the  plaintiff." Emmel, 95 F.3d at 630 (citing  EEOC v. G-K-G, Inc., 39 F.3d 740, 745  (7th Cir. 1994)). Although we review the  denial of a motion for judgment as a  matter of law de novo, our review of the  denial of MTD's motion for a new trial is  under the abuse of discretion standard.  Robinson v. Burlington Northern R.R., 131  F.3d 648, 656 (7th Cir. 1997).


52
With respect to MTD's claim that the  district judge erroneously excluded some  of its proposed expert testimony, it is  well established that a trial judge has  wide discretion in determining both the  competency of an expert witness as well  as the relevancy of the expert's  testimony on a particular subject.  Consequently, a judge's decision to limit  an expert's testimony "will be overturned  on appeal only if manifestly erroneous."  United States v. Lanzotti, 205 F.3d 951,  956 (7th Cir. 2000) (citation omitted).

B.  Sufficiency of the Evidence

53
As mentioned above, the plaintiffs'  theory of liability was straightforward.  The plaintiffs claimed that MTD was  negligent in the use of a plastic wing  nut to mount the rope guide because a  plastic wing nut was prone (and a steel  wing nut with nylon threading was less  likely) to become loose due to the  vibrations of a gas-powered lawn mower.  According to the plaintiffs' theory of  the case, the lawn mower's plastic wing  nut vibrated loose, was struck and sliced  by the mower blade, and was propelled at  a high rate of speed out the side chute.  After striking the lawn mower blade and  being discharged out the downward-facing  chute, the wing nut bounced off the  ground, struck the siding on the house,  and ricocheted into Goodwin's left eye.


54
In support of their theory, the  plaintiffs offered the testimony of three  people. Initially, Goodwin testified that  he was walking behind the mower while  cutting his grass and that the discharge  chute was facing downward as directed in  the instructions manual. He also stated  that after he had been mowing for  approximately 20 minutes, and was  approximately five feet from his house,  he was struck in the left eye by an  object. Finally, after his surgery,  Goodwin searched the area near the  accident and discovered a damaged plastic  wing nut which was sliced as a result of  its coming into contact with the mower's  blade. Furthermore, it should be noted  that after the accident and upon  inspection of the lawn mower, it was  discovered that the mower was missing a  wing nut and that the sliced wing nut  Goodwin recovered fit the lawn mower  exactly where the missing plastic wing  nut would have been.3 It is also  important to note that Goodwin was the  only eye-witness to the accident and,  obviously, the jury must have decided to  find his testimony credible concerning  where he was walking when he was struck  in the eye by the wing nut as well as the  position of the discharge chute at the  time of the accident. Any attempt by MTD  to argue that Goodwin's testimony was  insufficient to establish the  circumstances which lead up to the  accident is meritless because, as we have  long held,


55
[w]e will not second-guess a jury on  credibility issues. While this court's  review is confined to the "cold pages" of  an appellate transcript, the jury had an  opportunity to observe the verbal and  non-verbal behavior of the witnesses,  including the subject's reactions and  responses to the interrogatories, their  facial expressions, attitudes, tone of  voice, eye contact, posture and body  movements . . . . [I]t is not the task of  this appellate court to reconsider the  evidence or assess the credibility of the  witnesses.


56
Hasham v. California State Bd. of  Equalization, 200 F.3d 1035, 1047 (7th  Cir. 2000) (citing United States v.  Hickok, 77 F.3d 992, 1006 (7th Cir.  1996)).


57
Not only did the plaintiffs present  Goodwin's testimony, but they also  presented the testimony of two experts,  the board-certified ophthalmologist who  performed Goodwin's surgery as well as an  engineering expert.


58
According to Dr. Born,


59
the broken wing nut [in this case] is a  type of projectile consistent with the  injury to Mr. Goodwin's cornea. It  satisfies that criteria, being large  enough to cause a significant blow to the  eye and relatively sharp being cut by the  lawn mower to cause the slice and injury  to the eye.


60
Thus, the jury was informed by the  surgeon that the wing nut in this case  was the type of object that could  haveinflicted Goodwin's "very unusual"  eye injury.


61
Finally, the plaintiffs also introduced  testimony from their expert, Marty.  According to Marty's testimony, the wing  nut in this case evidenced that a slice  had been inflicted onto it as a result of  its coming into contact with the lawn  mower blade. Marty also testified that in  his opinion the manufacturer's design of  a lawn mower that used a plastic wing nut  was "defective and unreasonably  dangerous" because "the plastic wing nut  does not have a locking feature and it  can easily unthread if it should loosen."  Furthermore, according to Marty, a  plastic wing nut was more likely to come  loose due to the lawn mower's vibrations  than a steel wing nut with nylon  threading. Finally, Plamper's (MTD's  expert) original report opined that  "Goodwin's injury was not the result of a  direct hit but rather a ricochet."  Although Plamper attempted to recant his  previously stated opinion during trial  and claim that Goodwin's injury was the  result of a direct hit rather than a  ricochet, the district court judge aptly  noted that "in light of his obvious  incentive as the mower's designer to  testify in a way that would avoid  liability, the jury was free to determine  that he had it right the first time."


62
After reviewing the record, we are of  the opinion that the jury's verdict in  favor of Goodwin is sufficiently  supported by the evidence in the record.  Consequently, we agree with the trial  judge's rulings on MTD's motions after  the verdict and reject MTD's argument to  the contrary.

C.  Expert Testimony

63
MTD also argues that it is entitled to  a new trial because the judge committed  error in limiting the testimony of its  expert. Specifically, MTD argues that  Plamper should have been allowed to: 1)  introduce videotapes demonstrating what  needs to be done to a lawn mower after it  is purchased to make it operational; 2)  introduce videotape of him performing  various safety tests; and 3) testify as  to how he believed the accident occurred.


64
The trial judge summarized his  conclusions concerning MTD's proposed  expert testimony as follows


65
During Plamper's testimony at trial the  court sustained objections to his  testimony concerning the nature of  plaintiff's injury and whether it could  have been caused by the wing nut as  theorized by plaintiff. The objection was  sustained because there was no foundation  that Plamper had any medical expertise  which would enable him to competently  testify on the degree of injury which a  particular object could cause. It was  also sustained because Plamper's expert  report made no reference to any such  opinion. There was no other evidence  which would support an opinion that the  plaintiff must have been directly in  front of the chute. Accordingly,  Plamper's proffered testimony on that  issue was not expert testimony but  speculation and argument unsupported by  admissible scientific evidence.  Defendant's counsel was free to argue  that the accident happened in a different  way, but to give that argument the force  of expert opinion would have been  misleading to the jury and contrary to  the limits and purposes of expert  testimony.


66
Plamper testified at great length at  trial about thrown objects testing he  conducted on the mower. The jury was  fully apprised of the results of that  testing and Plamper's conclusions from  it. A video tape of the testing would  have been entirely cumulative, a  distraction and a waste of time. This is  even more apparent as it concerns the  videotape of the mower being assembled.  The actual mower was present in court for  the jury to examine. The assembly of the  wing nut could readily be demonstrated.  Nothing was to be gained by showing the  video of that process . . . .


67
Finally, Plamper was free to testify and  did testify about vibration testing on  the mower. He described the vibration  test, the result that nothing vibrated  from the mower and specifically offered  his opinion based on this test that a  properly tightened nut could not vibrate  from the mower. . . . The video tape of  vibration testing showing that nothing  vibrated from the mower would have added  nothing helpful to the jury, being  cumulative of the testimony and a waste  of time.

1.  Daubert

68
In Bourelle v. Crown Equipment Corp.,  220 F.3d 532, 536 (7th Cir. 2000)  (footnote in original), this court stated  that


69
[i]n the recent and well-recognized  Daubert v. Merrell Dow Pharmaceuticals  Inc., 509 U.S. 579, 589, 113 S. Ct. 2786,  125 L. Ed.2d 469 (1993), the Supreme  Court held that Fed. R. Evid. 702 imposes  on the trial court the obligation, when  dealing with expert witnesses, to ensure  that scientific testimony is "not only  relevant but reliable."4 In Kumho, the  Supreme Court clarified its decision in  Daubert and held that "this basic  gatekeeping obligation" applies to all  expert testimony. 526 U.S. at 147. Thus,  the trial judge must determine whether  [an expert's] opinion was grounded in the  "methods and procedures of science,"  Daubert, 509 U.S. at 590, 113 S. Ct.  2786, and whether such testimony had  sufficient "factual underpinnings,"  Walker v. Soo Line R.R. Co., 208 F.3d  581, 586 (7th Cir. 2000).


70
Furthermore, as the Supreme Court  elaborated


71
The objective of [Daubert's gatekeeping]  requirement is to ensure the reliability  and relevancy of expert testimony. It is to make certain that an expert, whether  basing testimony upon professional  studies or personal experience, employs  in the courtroom the same level of  intellectual rigor that characterizes the  practice of an expert in the relevant  field.


72
Kumho, 526 U.S. at 152. Also, "[i]t is  axiomatic that proffered expert testimony  must be 'derived by the scientific method  [.]'" Clark, 192 F.3d at 756 (citations  and internal quotations omitted).


73
2.  Plamper's opinion regarding the  cause of the accident


74
MTD attempted to introduce Plamper's  opinion regarding the cause of the  accident. Specifically, MTD wanted to  introduce Plamper's opinion: 1) that a  wing nut could not have caused the type  of eye injury Goodwin sustained; 2) that,  contrary to the plaintiff's testimony,  Goodwin was not in the operator's zone  (behind the lawn mower) when he was  injured; and 3) that the discharge chute,  which Goodwin claimed was facing down,  must have been facing up for the  plaintiff to have been injured in the  manner he described.


75
With respect to Plamper's testimony  concerning his opinion as to the  impossibility of a wing nut causing the  type of eye injury Goodwin sustained, we  agree with the experienced trial judge's  ruling that Plamper, an engineer, was not  qualified to give an expert opinion  concerning the nature, scope, or cause of  an eye injury that resulted from contact  with a wing nut which was discharged at a  high rate of speed from a lawn mower.  Plamper has neither a medical degree nor  any medical training, and an individual  with a degree in mechanical engineering  is not qualified to give expert testimony  on medical questions, including the cause  of an eye injury.


76
MTD also wanted to introduce Plamper's  "expert opinion" that he did not believe  Goodwin when he stated he was in the  operator's zone behind the lawn mower  with the discharge chute facing down when  he was injured. We agree with the trial  judge who properly concluded that,  although defense counsel could argue to  the jury that the accident occurred in a  different way, MTD was not entitled to  have an expert give an opinion as to the  veracity of Goodwin's testimony  concerning the circumstances surrounding  the accident when that opinion was merely  based on speculation and not on  admissible scientific evidence. Any argu  ment by MTD that Plamper was entitled to  give expert opinion as to whether he  believed Goodwin's testimony that he was  in the operator's zone behind the mower  with the discharge chute facing down is  without merit because an expert cannot  testify as to credibility issues. Rather,  credibility questions are within the  province of the trier of fact, in this  case a jury. Hasham, 200 F.3d at 1047  ("We will not second-guess a jury on  credibility issues.").

3.  The videos

77
MTD also argues that it is entitled to  a new trial because the trial judge  erroneously excluded, as cumulative,  videotapes it wanted to show to the jury.  Specifically, MTD wanted to show a video: 1) of a lawn mower being assembled; 2) of  Plamper running over various objects with  a lawn mower and how the objects were  discharged from the mower; and 3) of  vibration testing.


78
However, the decision that the  videotapes would be cumulative "rests  within the sound discretion of the  district court." United States v.  Gardner, 211 F.3d 1049, 1055 (7th Cir.  2000) (citing United States v. Kizeart,  102 F.3d 320, 325 (7th Cir. 1996)). And,  as we stated in Gardner,


79
[e]vidence is 'cumulative' when it adds  very little to the probative force of the  other evidence in the case, so that if it  were admitted its contribution to the  determination of truth would be  outweighed by its contribution to the  length of the trial, with all the  potential for confusion, as well as  prejudice to other litigants, who must  wait longer for their trial, that a long  trial creates.


80
Id. at 1055 (quoting United States v.  Williams, 81 F.3d 1434, 1443 (7th Cir.  1996)).


81
With respect to the video of the lawn  mower being assembled, we agree with the  trial judge that the use of such  demonstrative evidence from a videotape  would have been cumulative because the  lawn mower was in plain view of the jury  and, as the district judge stated, "the  assembly of the wing nut [in question]  could be readily demonstrated."  Furthermore, Plamper essentially  testified as to what was necessary in  order to make the lawn mower operational  after purchase, including the tightening  of the wing nuts. We are convinced that  the video demonstrating the assembly of  the lawn mower would be cumulative and,  thus, a waste of the court's and the  jury's precious time. The trial judge's  decision to exclude the videotape was  proper.


82
MTD also wanted to introduce a videotape  of Plamper performing a "thrown object  test."5 Essentially, the videotape  demonstrates Plamper steering the lawn  mower (with the motor operating) over a  variety of objects and how those objects  are discharged out the lawn mower.  However, Plamper was allowed to testify  at great length as to the "thrown object"  tests he performed and the results that  were reached. Furthermore, the jury was  fully apprised of Plamper's conclusions  as a result of the thrown object testing.  As this and other courts have held, a  trial judge's decision to exclude a  videotape of essentially the same subject  matter material that the expert had just  testified to is not an abuse of  discretion and does not warrant a new  trial. See, e.g., Finchum v. Ford Motor  Co., 57 F.3d 526, 530-31 (7th Cir. 1995);  United States v. Falcon, 766 F.2d 1469,  1477-78 (10th Cir. 1985); United States  v. McCollum, 732 F.2d 1419, 1423 (9th  Cir. 1984). Consequently, the trial judge  properly excluded the videotape as  cumulative.6


83
The exact same analysis used above can  be applied to the videotape regarding the  vibration testing performed by Plamper.  Despite MTD's arguments, a review of the  transcripts reveals that Plamper  testified, at length, concerning his  opinion that the plastic wing nut would  not come loose due to vibrations if  properly tightened. Allowing MTD to  introduce a videotape of a lawn mower  operating and the wing nut not vibrating  loose is not only cumulative of Plamper's  testimony but also a waste of the jury's  and the court's time. Cases like Finchum,  Falcon, and McCollum mandate that the  judge's decision to exclude the videotape  of the vibration testing be upheld.


84
We are convinced that the plaintiffs  offered evidence sufficient to support  the jury's verdict. Furthermore, we are  of the opinion that the trial judge did  not erroneously exclude any of the  videotapes MTD wanted admitted nor did  the judge improperly limit the scope of  Plamper's testimony.

The decision of the district court is

85
AFFIRMED.



Notes:


1
 Although Goodwin was wearing glasses at trial, he  testified that he was not wearing any glasses at  the time of his accident.


2
 MTD and the Goodwins agreed to have the trial  judge read a short narrative as to each of the  expert's qualifications. Consequently, there was  no direct testimony as to the expert's qualifications.


3
 Marty opined that the damage to the wing nut was  "very consistent with contact with a sharp object  such as a lawn mower blade" and that the "cut  would have been made once the wing nut detached  from the mower and was no longer protected by the  handle that it was at one time likely secured  to." In fact even MTD's expert admitted that the  damage to the plastic wing nut was consistent  with having been hit by the mower blade.


4
 Daubert set forth the familiar nonexhaustive list  of four factors that are helpful in gauging the  reliability of expert testimony: 1) whether the  theory is scientific knowledge that will assist  the trier of fact and can be tested; 2) whether  the theory has been subjected to peer review or  publication; 3) the known or potential rate of  error and the existence of standards controlling  the technique's operation; and 4) the extent to  which the methodology or technique employed by  the expert is generally accepted in the scientific community. See Daubert, 509 U.S. at 593-94,  113 S. Ct. 2786. However,
[b]ecause the Daubert Court "emphasized that it  did 'not presume to set out a definitive check-  list or test,' and that the district judge's  inquiry should be 'flexible,'" United States v.  Vitek Supply Corp., 144 F.3d 476, 485 (7th Cir.  1998) (citation omitted), there is no requirement  that the district judgeconsider each one of these  "guideposts" when making an admissibility ruling  under Fed. R. Evid. 702.
Ancho, 157 F.3d at 515.


5
  The thrown object test is merely a variety of  objects being run over by a lawn mower and  discharged out the side chute.


6
  We also believe that the proposed thrown object  test evidence was irrelevant to the plaintiffs'  case. The tests were performed with a different  lawn mower, at a different location, in different  mowing conditions, and ricocheted off a different  house with different siding and foundation.  However, given that the trial judge properly  excluded the videotapes as cumulative, we need  not address this issue.


