The California Court of Appeal recently had occasion to review certain forensic video analysis techniques employed by a forensic expert for the purpose of determining whether they were properly admitted at trial and additionally whether they constituted novel science, thus requiring a Kelly-Frye hearing.
In People v. Tran, 2020 WL 3056213, the state presented evidence from a qualified forensic video analyst who undertook technical processes including image clarification, interpretation of infrared camera image differences, alignment of multiple video sources, aspect ratio correction, and motion tracking. The expert described his analysis in detail, noting a proper audit trail of all processes undertaken, reproducibility by other competent analysts, and peer review. Further, he wisely offered no opinions on use of force and identified no one as the perpetrator, recognizing his proper role in the case. He also articulated why it would be difficult for the trier of fact to properly interpret the video evidence without the assistance provided.
The defense argued that “forensic video enhancement is not universally accepted and the law is not clear,” and that the processes employed by the expert should be evaluated under Kelly-Frye. The defense further argued that it was unnecessary to present expert evidence given “that the jury can see for itself.”
The trial court concluded that, “It is clear to me that the testimony of the witness would assist the trier of fact, and that not only would it assist the trier of fact, I think it is quite necessary to assist the trier of fact.” Regarding motion tracking, the trial court found that tracking multiple subjects accurately would be “impossible…and even with his assistance, very difficult.” On the Kelly-Frye issue, the trial court declined to conduct an admissibility hearing as the expert’s evidence did not reveal a novel scientific testing method or procedure.
On appeal, the Court of Appeal stated that trial judges bear a substantial responsibility to ensure that expert testimony is utilized correctly. Evaluating the expert evidence presented at trial, the Court likened it to “computer animation” with a correlation to demonstrative evidence. The Court noted that the expert did not alter the video evidence, rather, he enhanced the quality of what was already present. The motion tracking utilized was easily understood, was not novel, and was provided to assist the jury in wading through complex motion video from numerous sources. The Court found the expert evidence to be relevant, useful, and highly probative as it assisted the jury in interpreting the video evidence. The Court endorsed the trial court’s view that without the motion tracking evidence, it would have been very difficult, if not impossible, for the jury to comprehend the evidence on its own. Regarding both motion tracking and video alignment, the Court noted that these techniques “were critical for the jury to make sense of the various videos that differed by way of time stamps, camera angles, dimensions, lighting, resolution, pixel ratios, and quality.” The Court concluded by ruling that the trial court had not abused its discretion in admitting the video evidence, along with the expert evidence presenting and interpreting it for the jury. Accordingly, the evidence was properly admitted.
Analysis
I am currently working on a PhD in law at Leiden University in the Netherlands. My area of research and writing is “The Visualization of Digital Evidence in International Criminal Prosecutions.” While my focus is on visualization in the context of prosecutions for genocide, crimes against humanity, war crimes, and crimes of aggression, much of my work applies at the national level as well. I am currently writing a dissertation chapter entitled “The Picture Does Not Speak for Itself: Expert Interpretation” and so the Tran case caught my attention.
The defense argued that expert evidence was not necessary, “that the jury can see for itself.” This statement is reflective of the paucity of visual literacy that exists among many members of the legal profession and the judiciary. Both attorneys and judges must be educated regarding the challenges of competently evaluating visual evidence. Absent sufficient visual literacy, the viewer is unlikely to understand and grasp the full significance of the image. Expert analysis of images and video may bring out details not otherwise noted and may provide a level of understanding unachievable without advanced technical visual literacy.
Pictures do not speak for themselves. We must use words to evaluate their content, with the express caveat that pictures cannot necessarily be reduced to words, as they may mean more than they actually say. Feigenson (2014) notes, “Thus, perhaps ironically, the more the law depends on pictures, the more it needs words about those pictures: to affirm or dispute their authenticity, to frame their meanings so that they can be deployed to explain and persuade, and to subject them to reflection and critique.”
While the democratization of assigning meaning to images is unavoidable, people who must make decisions based upon them should not be left to their own devices to understand image content and meaning. Visual literacy should not be assumed. The images that were tendered in Tran were semi-legible, meaning that they were neither entirely legible, nor impossible to read. “Semi-legible images cannot be said simply to speak for themselves; they must be made to speak, through the exertion of effort, expertise, or both.” (Mnookin: 2014)
There is a naïve tendency for viewers to believe that they have properly digested an image. This sense of communicative efficacy is even stronger with sequential moving images. Giving undue credence to images will lead to injustice “as judges assume that the camera provides them with an unmediated perception of events, a perception that is necessarily the product of their own experience.” (Mezey: 2013) Video evidence is often open to interpretation and should be critically examined in the same manner as eyewitness testimony. Failure to do so risks assigning meaning to an image without necessarily understanding it.
Looking at an image holistically can provide context and meaning about what is depicted, if properly understood. If we consider that an image is a conglomeration of many sub-images, then detailed analysis of those constituent elements may yield information on specific issues, including identification of people and objects in the image, details of movement, the presence of a weapon, infliction of injury, etc. This may involve detail at the pixel level, which would likely be missed without expert image interrogation and interpretation.
“If the legal profession remains visually illiterate and fails to appreciate the many ways images speak, as well as the limitations of what those images can say, it risks sacrificing the crucial role of the law in interpretation, judgment, and justice.” (Mezey: 2013) The risks are palpable and include misinterpretation, the failure to find the truth, and an unjust outcome. Counsel can improve their visual literacy, and in turn, that of the court, by utilizing competent experts in the analysis and presentation of video evidence. Forensic examination of an image requires that the image be confronted by someone with the skills necessary to dissect and reconstruct the image in order to maximize its evidential value. The end result may be an appreciation of the image’s true import, far from that initially held by counsel and the court. By allowing testimony based on evidence-based research, peer review and professional credentials, the law becomes more responsive to reason. Visual evidence is thus more likely to contribute scientifically valid truths, rather than junk science.
In Tran, while it is debatable whether the trial judge was correct to state that the expert’s work did not involve science, and further debatable whether the Court of Appeal was correct to liken the expert’s evidence with computer animation and demonstrative evidence, both courts correctly determined that the jury was ill-equipped to evaluate this complex video evidence without expert assistance. The defense’s myopic comment that the jury can see the video for itself is reflective of a lack of visual literacy that plagues the legal community. Having prosecuted criminal cases for over thirty years, many with expert forensic video analysis evidence, the refrain of opposing counsel that we all have eyes and don’t need any expert telling us what we see is an endemic, uninformed refrain. The goal of any criminal prosecution should be to thoroughly interrogate and interpret the evidence for the purpose of determining the truth. In Tran, the expert witness assisted the trial court in doing just that and in improving the visual literacy of those involved in the case.