Admissibility of Photogrammetric Evidence – Trial Court is a “Gatekeeper” But Not an “Armed Guard”

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Two people were murdered.  It was late at night in an area of known drug deals.  There were witnesses, but many had consumed legal or illegal substances and others were inconsistent.  There was video, but not of the shooting.  The Court called it “incomplete.”  An FBI analyst testified to a photogrammetric analysis of the video, but admitted that certain variables precluded calculating a definitive margin of error.

The Court of Appeals stated that:  “The challenge for everyone lay in piercing together fragments of evidence that took many different forms.”  State v. Matthews, __ Md. ___, 2022 WL 2236139 (June 22, 2022)(citation omitted). The Court described its decision as its “first opportunity” to review admissibility of expert testimony under the Daubert standard it had adopted in 2020.

The Court emphasized that the trial court’s gatekeeper role is to determine whether the expert’s methodology was sound and whether it was applied to an adequate amount of data. If those predicates are present, expert testimony should not be excluded due to a concern that the conclusions may be inaccurate.  The Court held that the evidence was admissible and affirmed the conviction.

One central piece of evidence was electronically stored information – the video.  Some of the State’s evidence turned on photogrammetric analysis of the low-quality video.

[The FBI analyst] explained that “photogrammetry is just a very long word that means we’re trying to make measurements in photos.” She further testified that there are two basic forms of photogrammetry: (1) reverse projection photogrammetry, which requires going to the place where the questioned image was created and “duplicating the imaging conditions that captured the original scene in order to make a measurement”; and (2) analytical photogrammetry, which relies on software to make measurements based on the image itself, and does not require going to the scene. According to [the FBI analyst], software-based photogrammetry is less accurate than reverse projection photogrammetry.

Id. at *4.

Based on photogrammetric analysis, the FBI expert testified that the person carrying a shotgun in the video was 5’8” tall, with a margin of error of “plus or minus two-thirds of an inch.”  Id. at *4.[1]  However, the FBI analyst also testified that:

“[T]he degree of uncertainty in this measurement could be significantly greater” based on several variables, including “the subject to camera distance, the resolution of the imagery, the unevenness of the landscape, and the body position of the subject.” [The FBI analyst] testified: “I don’t have a scientific way of quantifying how those dimensions had an effect on my measurement and consequently I wanted in an abundance of caution to mention them.” [emphasis added].

Height was an issue, with one witness having observed a person who was 5’11” at the scene. The defendant – Matthews – was 5’9” tall.  He objected to introduction of the FBI analysis.

The defense presented two challenges to admissibility.  The first was under Daubert and Md. Rule 5-702. The second was that the prejudice outweighed the probative value under Md. Rule 5-703.

The Court’s decision describes at length the FBI analyst’s methodology, which included a site visit roughly six months after the shooting.  Id. at *4, passim. It also summarizes the conflicting testimony of defense experts.

The Court explained that no single factor is dispositive of a Daubert analysis under Rule 5-702.  Certainly, one factor is whether there is a known or potential rate of error.  Matthews, 2022 WL 2236139, at *14-15.

The Court also wrote that conclusions and methodology are not entirely distinct and here the FBI analyst’s methodology was reliable:

There is no dispute that [the FBI analyst]’s methodology was reliable. Nor was there any analytical gap in her proffered testimony. The unknown degree of uncertainty concerning the accuracy of [the FBI analyst]’s height estimate went to the weight the jury should give to the expert testimony, not to its admissibility.

It then explained:

Matthews fails to appreciate the distinction between uncertainty inherent in an expert’s methodology and uncertainty that applies to an expert’s conclusions following the application of a reliable methodology. If an unacceptably high margin of error exists whenever a particular scientific technique is applied or no error rate can ever be determined with respect to that technique, a trial court may well decide to exclude testimony concerning the application of such a technique. In that situation, the court is concerned about the inherent unreliability of the expert’s methodology, i.e., the unacceptably high risk of an inaccurate conclusion being reached in every case where the technique is used. A different situation applies where an expert applies a reliable technique to an adequate supply of data, but in reporting her results, states that she is unable to quantify a specific degree of uncertainty/margin of error. That scenario is generally less problematic than where an expert has applied a technique that is unreliable in every instance in which it is used.

 For these reasons, in exercising its gatekeeping function under Rule 5-702, a trial court generally should be most concerned about the reliability of an expert’s methodology. Once a trial court is satisfied that an expert has applied a reliable methodology to an adequate supply of data, the court should not exclude the expert’s testimony merely because the court is concerned that the expert’s particular conclusions may be inaccurate. [emphasis added].

Here,  the Court determined that the FBI analyst “applied her reliable technique to an adequate supply of data.” Id. at * 18.

The Court gave some examples of an inadequate data supply.  If there is a small sample size, improper calibration of a testing devices, or lack of a known error rate (as in polygraphs), those data are not adequate.

It rejected the “analytical gap” challenge.  There is a fatal “analytical gap” only where the expert is unable to bridge a gap between the opinion and the empirical foundation for it.  Id. at *18.  That was not the case here:

There was no disconnect between the results of the photogrammetry analysis and [the FBI analyst]’s opinion. The underlying height value was based on the calibrated height chart in the overlay image, and the 0.67 inch margin of error was based on calculations that went essentially unchallenged. To this extent, [the FBI analyst]’s height estimate was the result of combining “generally accepted methodology” with “generally accepted analysis.”

The Court then turned to the argument that the probative value was outweighed by the prejudice.  That Rule 5-403 argument was derivative to the Daubert argument.  Essentially, Matthews argued that because the height estimate was unreliable, the prejudice outweighed the probative value.

However, the trial court stated that all evidence is prejudicial and here the issue was whether it was “unfairly” prejudicial.  It held that all of the qualifiers were available to the jury and the trial court did not find it confusing or unfair.

That was affirmed.  The appellate court held that the lower court had properly assessed the expert’s rigor and care.  The expert had explained why “despite the unknown degree of uncertainty attributable to certain variables, she nevertheless was comfortable with her height estimate of 5’8” plus or minus two-thirds of an inch.”  Id. at *20. The jury had heard cross-examination, a defense expert, and closing argument.

All of these factors allowed the trial court to reasonably conclude that the height estimate of the subject as 5’8” plus or minus two-thirds of an inch would assist the jury in determining the identity of the person in the questioned image, despite the fact that [the FBI analyst] could not calculate the effect of all variables on the degree of uncertainty.

Id. at *20.

Importantly, the Court reiterated the role of the trial court.  It wrote:

Our conclusion respects the trial court’s role as a “gatekeeper,” and does not transform the trial court into an “armed guard.” [citation omitted]. “As long as an expert’s scientific testimony rests upon ‘good grounds, based on what is known,’ it should be tested by the adversary process – competing expert testimony and active cross-examination – rather than excluded from jurors’ scrutiny for fear that they will not grasp its complexities or satisfactorily weigh its inadequacies.”

Id. at *21 (emphasis added).[2]


[1] I used photogrammetric evidence in a civil police shooting lawsuit with great effect.  Waterman v. Batton, 393 F.3d 471 (4th Cir. 2005)(holding officers shown in video had qualified immunity).

[2] Notably, as the dissent pointed out, the case was tried under the Frye-Reed standard; however, the Court of Appeals adopted the Daubert standard retroactively.

The dissent focused on what it viewed as an analytical gap:  “It will not be the case that an analytical gap will exist in every instance in which an expert cannot account for unknown facts. But in this case unknown information, such as the condition of the terrain on which the person stood, the distance of the person from the camera, and the positioning of person’s body, and the poor quality of the photograph at issue, created an analytical gap that the expert herself recognized when she acknowledged that she had no way of calculating the effect that the missing information had on the outcome of her measurements. Although the expert indicated that she felt comfortable with her analysis, the missing variables concerned core information that an expert performing a reverse projection photogrammetric analysis would have needed to render a reliable opinion.”