From Boyd v. City and County of San Francisco, 576 F.3d 938 (9th Cir. 2009):

In disputing the relevance of the challenged evidence, the Boyd Family target Dr. Keram's expert testimony in particular. They assert that the district court failed in its role as a gatekeeper of the evidence by allowing Dr. Keram's testimony regarding suicide by cop. ***

After a lengthy hearing outside the presence of the jury in which both parties had the opportunity to examine Dr. Keram, the district court admitted her testimony. The trial judge, noting that she "started out rather skeptical of this whole subject[, a]nd in particular, its application to this case," ultimately concluded that Dr. Keram was "a principled witness" with highly trained expertise, who did not appear "to be favoring one side or the other."

The district court then examined Dr. Keram's testimony using each of the four Daubert factors. The court noted that while the suicide by cop theory could not be tested "in the sense of running a scientific experiment[,] . . . there have been a number of studies conducted" supporting the validity of the theory. Those studies analyzed the methods used in the field of psychiatric forensics for attempting to reconstruct an individual's state of mind after the fact, based on evidence of his actions and his surrounding circumstances. Dr. Keram testified that the studies performed under this method were extremely strict in their requirements, to guard against the registering of false positives. Dr. Keram was careful to tie her conclusions in this case to the literature on suicide by cop, noting recognized factors or connections supporting her opinion. Dr. Keram testified to knowing of approximately ten peer-reviewed articles and four non-peer-reviewed publications on the subject. Regarding the rate of error for the theory, the court noted Dr. Keram's testimony that the selection criteria used in the relevant studies erred heavily on the side of exclusion, designating situations as an example of suicide by cop only if they met a very high bar. Finally, the court noted that the theory appeared to be generally accepted in the relevant professional community, with a high number of publications written in support of the theory and no contrary articles or studies. Based on these factors, the court concluded that the testimony satisfied Daubert's requirements for admission.

[Footnote 5] We acknowledge that both the Fifth and Seventh Circuits have also made reference to the suicide by cop theory. See, e.g., Hainze v. Richards, 207 F.3d 795, 797 n.1 (5th Cir. 2000); Plakas v. Drinski, 19 F.3d 1143, 1146 (7th Cir. 1994).

The Boyd Family seeks to challenge the district court's conclusion by attacking the validity of the theory, but provides no scientific opinions challenging or refuting it. Indeed, they present no evidence, outside of their own assertions, that the theory is unreliable, nor do they dispute the existence of multiple peer-reviewed articles in support of the theory. They criticize the methodology used to test for possible suicide by cop, but present no alternative, more reliable methods, nor their own expert to rebut Dr. Keram's conclusions. Finally, they challenge Dr. Keram's conclusions by asserting essentially that, had they been the experts, they would have reached a different conclusion based upon the evidence.

Daubert makes clear that the role of the courts in reviewing proposed expert testimony is to analyze expert testimony in the context of its field to determine if it is acceptable science. "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." Kumho Tire Co., 526 U.S. at 152. In this case, the district court was satisfied that Dr. Keram's testimony regarding suicide by cop "pass[ed] muster." Based on our review, we agree, and conclude that the district court did not abuse its discretion in admitting Dr. Keram's testimony.