A fundamental question in the forensic process of image comparison is what qualifies a proposed expert to express such an opinion for the court’s consideration. Various contenders ranging from people with no qualifications whatsoever, to wedding videographers, production video specialists, experts from the non-imaging world, and certified forensic video analysts have appeared in courtrooms to provide expert image comparison evidence. It falls upon the court to determine if the proposed expert testimony should be permitted. This article is about one such case in California.
In People v. Pratt, 2022 WL 99236 (Court of Appeal, 2d Dist., California), at issue was whether the witness called by the state to provide image comparison evidence should be allowed to testify as an expert witness. The witness would compare “grainy” enlarged CCTV images of the shooter with images of the defendant taken by the police while in custody as well as “a very grainy image of the pants worn by the shooter and a high-resolution image of the pants taken by the police” from the defendant’s bedroom. The defence made a pre-trial motion to exclude the proposed evidence on the basis that the jury did not require assistance and that the witness lacked the necessary expertise. The state countered by saying that since the witness would only discuss similarities and would not offer a conclusive opinion, the testimony should be allowed.
The Section 402 Hearing
The issue was not resolved pre-trial and the defence objection was renewed at trial. The state asserted that the witness would compare the facial features of the shooter and the defendant and state that they were “similar”. Regarding the pants, the witness would state that “in her educated opinion”, they “are one and the same” and would explain how she reached that conclusion. The defence argued that this was not expert opinion evidence as the witness had not done any facial measurements, had not enhanced the video images, and generally had not done anything that an expert would do. The defence further argued that the witness was being tendered as a forensic graphic artist, a field of expertise that is not part of forensic science or science in general. Accordingly, an Evidence Code Section 402 hearing was held in the absence of the jury.
The proposed expert testified that she is a forensic artist and graphic designer. As a graphic designer she had experience in designing graphics for clothing. As a forensic artist, she had training in illustration, rendering, and anthropology. She had further in-service forensic artist training while at the Los Angeles County Sheriff’s Department. From there she “learned how to work from video and look at images and…clarify for a detective what those images may look like and possibilities thereof.” She is a member of the American Academy of Forensic Sciences and had taught forensic art to law enforcement agencies. She worked as a graphic arts coordinator and lead forensic artist for over 25 years for the Sheriff’s Department where she drew composite images and created facial reconstructions from skeletons. She also had experience with photo editing software and used that to make photographic lineups more “fair”. In the present case, the images she relied upon were not enhanced and she undertook no facial measurements. The trial court allowed her to testify in an expert capacity.
Trial Testimony
At trial, the (now qualified) expert testified that she compared the known images of the pants to the questioned CCTV images. If the court’s description of this is correct, then the expert examined the images in the incorrect order as an expert should always start with the questioned images to mitigate bias. She then compared the CCTV images of the shooter to the known images of the defendant. Her opinion was that the person showed in the CCTV and known images were similar and articulated what facial features supported her view. The pants shown in the images were also declared to be similar (contrary to the conclusive opinion earlier asserted by the state). In cross examination, the expert acknowledged that the brand name noted on the pants in the known images was not visible in the questioned images. She also agreed that the facial features she noted were common in the Black community.
The defence presented their own “audio and video forensic expert” who testified that he followed SWGDE guidance when he undertook his comparisons. He noted that while there were similarities between the questioned person and the defendant, there was also notable differences, which he pointed out to the jury. He also found both similarities and differences in the pants. The defendant was convicted of murder.
The Appeal
On appeal, the defence argued that while the witness had expertise in forensic art and graphic design, she was not qualified in image comparison of people and clothing. The Court of Appeal stated, “Although Enslow’s qualifications were not particularly impressive and the evidence of her credentials was thin, we cannot say she lacked the qualifications to enable her to testify about the similarities between the images in the surveillance videos and the photographs.” The Court noted that in most cases involving image comparison, the expert processes and clarifies images to assist the jury in their task. That is not what happened here.
The Court stated, “Enslow did not manipulate or enhance the video she reviewed, create new images based on forensic expertise to enable the jury to extract certain information from the surveillance video, or use any knowledge of video or photographic imaging to interpret the surveillance video. She merely looked at and compared the same surveillance video, and the same photographs of Pratt and his jeans, the jurors also saw. Under these circumstances, Enslow’s testimony at least came dangerously close to invading the province of the jury.”
The Court was more inclined to find error in the admission of the comparison evidence about the faces since the witness offered nothing that assisted the jury in their task. The Court was less inclined to find error regarding the pants since the witness offered testimony about why a brand name might be visible in one image but not the other and noted that this was beyond the knowledge of the jury. The Court found that any error in admitting the comparison evidence was harmless given the strength of the state’s case, meaning that the evidence did not contribute to a conviction that was not otherwise obtainable. Further, the witness’s similarity opinion would not have bound the jury to decide in favour of the state, especially in light of the competing expert evidence. Proper cautions were given by the trial judge to the jury as to how to evaluate expert evidence. In short, while some of the expert’s evidence should have been excluded at trial, there was not harm in the result as the evidence in the case overwhelmingly supported the jury’s verdict.
Commentary
On the facts of this case, allowing the state’s witness to testify in an expert capacity did not materially contribute to the conviction and no miscarriage of justice occurred on that basis. However, it does give rise to a discussion of who should be called upon to express an expert opinion for the court. An expert witness is someone who through education, training, and experience has gained specialized knowledge in a particular subject and who applies that knowledge in a legal setting. The bar is not particularly high, but it must be shown that the expert brings to the table something the trier of fact lacks. In this case the state’s witness did not meet the bar for facial comparison and only barely cleared it for the pants comparison.
Image comparison is a scientific process that requires demonstrable expertise in imagery and comparisons. Images are complex factual constructs that must be confronted by someone with the knowledge to interrogate and interpret them to make reliable conclusions about their content. Are the images reliable? Are there technical issues such as compression, resolution, and interpolation that impact upon the assessment of image features? The court is entitled to an expert witness who can competently assess, process, and evaluate images, and has specific image comparison training. Forensic image comparison is not just a case of someone looking at images and looking for similarities and differences. The search for the truth mandates more than that. Counsel must seek out witnesses who are truly qualified so that they can present a compelling opinion, not one that is easily dismissed by the court.