**5. Australian authority**

*Forensic Analysis - Scientific and Medical Techniques and Evidence under the Microscope*

unreliable because:

of gait;

at [73]).

the material on which it was founded';

image rendered his opinion unreliable or unsafe:

*the cross-examination of Mr. Francis ([15] at [74]).*

each significant image' ([15] at [75]).

characteristics of gait from CCTV [22] and a Home Office Manual [23] in relation to the screen height on CCTV necessary to discern characteristic detail. It noted that at trial no challenge was made to Mr. Francis' evidence, notwithstanding the view of Mr. Blake. The argument was mounted, though, that Mr. Francis' evidence was

1.he provided his opinion 'in a manner that was overconfident having regard to

2.the material itself was inadequate for the purpose of identifying features

make and was unable to explain what allowances he had made; and

3.the expert was not qualified to make the 'allowances' he claimed to be able to

4.the value of the evidence was overstated by references to population ([15]

The Court of Appeal accepted that the quality of the CCTV images 'is at times indifferent' and that care is required to ensure that the feature demonstrated is reliably demonstrated ([15] at [74]). The Court did not accept that Mr. Francis' inability to specify in scientific terms how he made allowances for an imperfect

*He and the jury were viewing moving and still images. Mr. Francis was showing to the jury the images in which he saw features of gait and either those features could be seen by the jury or they could not. The jury was directed that they could act on the presence of features only if they could observe the features for themselves. Mr. Francis was saying that he had taken account of the imperfection in the image before declaring his identification of a feature. He showed the jury the image on which he relied to make the identification. He was not saying that, although the feature might not be seen by the jury, he, relying on his expertise, was sure it was present. In any instance in which it was argued that the quality of the image was insufficient to be sure that the feature was present the jury had the means to make the assessment for themselves with the assistance of the evidence of Mr. Blake and* 

This led the Court of Appeal to conclude that with appropriate judicial instructions the jurors could follow the evidence, evaluate its cogency and make their own decision as to whether the features demonstrated were present in each of the recordings. The Court did not agree with the argument that Mr. Francis should not have been permitted to refer to the frequency with which the features or abnormalities he found in the recordings occurred in the course of his clinical practice: 'It was for the jury to evaluate Mr Francis' evidence in the light of the criticisms levelled at him ([15] at [74]). Thus, it concluded that it was not necessary for the judge to have withdrawn the case from the jury at the close of the prosecution case – 'The jury had been provided with the tools with which to make that assessment: in the case of each image on which Mr Francis relied they had their attention drawn to the factors relevant to it, in particular to the quality of the images and the time lapse by which they were recorded. Mr Francis was closely cross-examined on each feature and

Both the *Otway* and *Hashi* decisions by the Court of Appeal determined the forensic gait analysis evidence to be admissible and that the risk of inappropriate

**12**

The most significant Australian authority on forensic gait analysis is the 2020 ruling by Justice Beale in the murder case of *The Queen v Crupi* [16]. Part of the evidence suggesting that Crupi was the murderer was forensic gait analysis evidence given on this occasion not by a podiatrist but by Professor Marcus Pandy, the Chair of Mechanical and Biomedical Engineering at the University of Melbourne. He viewed 95 CCTV clips and was asked to identify and document any physical characteristics viewed in them. He measured certain spatio-temporal features of the gait of the subjects using a Google Earth measurement tool – step length, step frequency and walking speed. He found the step lengths of the subjects were consistently around the same value. In his first report he did not express any opinion as to whether or not the subjects of the clips were the same person but concluded that the mean step length and mean walking speed of the subjects were more consistent with the persons being elderly, as was the degree of toe-out gait – the relevance of this to the prosecution was that Crupi was aged 67 at the time of the murder.

On the basis of the first report by Professor Pandy, he was asked to offer a further opinion as to whether 'a person recorded in any of the CCTV footage contained in clips 1 to 36 is the same as a person recorded in any of the CCTV footage contained in clips 37 to 95'. Police also provided more precise measurements between various geographical features shown in the clips so that Professor Pandy could calculate the relevant spatio-temporal gait features of the subjects more accurately, rather than relying on the Google Earth measuring tool. Professor Pandy concluded that the subjects walked with a gait pattern 'more consistent with that exhibited by older adults, who take shorter steps and walk more slowly than healthy young adults' (at [26]).

The cross-examination of Professor Pandy proved important. He disavowed being an expert on whether persons were similar or dissimilar and said he had never done any research regarding the pitfalls in making such a comparison. He said he was not familiar with the concept of confirmation bias ([16] at [29]). Professor Pandy said he was not a statistician but had sufficient knowledge of statistics to calculate standard deviations. He said there was no way of assessing whether the subjects in any of the clips were walking at their preferred speed and agreed that sometimes he had had to round down the number of steps taken between the relevant locations. He also conceded that he sometimes had to make a judgement as to when a subject's heel struck the ground ([16] at [32]) and that the subjects did not always walk in a straight line between the points. He sometimes observed excessive lateral movement in the gait of the subjects ([16] at [33]).

Professor Pandy said he had never previously been asked to compare CCTV clips of subjects, that he knew nothing about the make or model of the CCTV cameras capturing the relevant images or whether they distorted the images. He conceded he had no information about the frame rates of the CCTV clips and agreed that the frame rates could affect the accuracy of his judgements as to when the heel of the subjects struck the ground (at [34]). Importantly, Professor Pandy was not able to shed any light on the statistical significance of his findings compared with the population at large, and did not purport to do so, instead stating that the mean step lengths of

the subjects in the two groups of clips were 'remarkably similar' ([16] at [35]). He refrained from attributing any specific age estimate to the subjects.

He observed that both feet of the subjects exhibited toe-out gait, although he did not make measurements of it. He stated that it appeared greater than normal for healthy young adults but he did not know the prevalence of a greater than normal toe-out gait in the community ([16] at [37]).

Justice Beale declined to admit the evidence of Professor Pandy. He reviewed the relevance of the evidence by evaluating the potential for a jury to have rationally accepted the reliability of Professor Pandy's calculations. He noted the defects in his evidence about 'rounding-offs' and observed that they may have been concentrated in one group (at [85]) and noted too that Professor Pandy had conceded that the CCTV frame rates, about which he said he knew nothing, may have affected the accuracy of his subjective judgements. He was troubled too that Professor Pandy used the time stamps on the CCTV clip to make his calculations but did not check the accuracy of the various stamps for the various CCTV cameras, as well as the fact that the subjects did not always walk in straight lines between points A and B and that at times there was excessive lateral movement by the subjects. He agreed with the submission from the prosecution that none of these matters may have significantly affected the accuracy of Professor Pandy's calculations but found that 'there is no way of knowing whether that is the case' (at [86]). That led Justice Beale to conclude: 'If the jury is to act rationally, there must be a proper basis for the jury to conclude that the accuracy of his calculations were not significantly affected by these matters. The evidence fails to provide a proper basis for such a conclusion' ([16] at [86]). He was also troubled by what he described as the difficulty of concluding rationally that Professor Pandy was 'comparing apples with apples':

*He conceded in cross-examination that there was no way of knowing whether the subjects in clips 1–95 were walking at their preferred speed. And yet he based his opinion that the subjects had gait patterns more consistent with older persons primarily on a comparison of the data with results obtained in gait studies of young and old adults whom it was known were walking at their preferred speed ([16] at [87]).*

These issues led him to rule that the evidence of Professor Pandy failed the relevance test under s55 of Australia's 'uniform evidence legislation' and this made it inadmissible. The test in this regard was whether it had the potential to rationally affect the existence of a fact in issue between the prosecution and the defence.

In addition, Justice Beale was at pains to identify the area of specialised knowledge that the prosecution was seeking to adduce. He concluded that it was 'forensic gait analysis of subjects recorded on CCTV footage', this descriptor ultimately being important. He found that the fact that Professor Pandy conceded he was a novice in relation to the task of comparison – whether any of the subjects were the same – and also the CCTV aspect was significant. Professor Pandy conceded that had never undertaken gait analysis using CCTV recordings ([16] at [94]). Justice Beale found Professor Pandy's failure to discuss dissimilarities of gait to be a significant omission in his evidence and that it called into question his expertise to undertake comparative gait analysis. In addition, Justice Beale emphasised that Professor Pandy had conceded that it was the first time that he had conducted forensic gait comparison of subjects recorded on CCTV footage – 'it is difficult to see how Professor Pandy can be considered an expert in that field when this is the first time he has performed the task. For all his undoubted learning and experience,

**15**

*Guarding the Gait: Evaluating Forensic Gait Analysis Evidence*

I am not satisfied that Professor Pandy is an expert in the relevant area of FGA ([16] at [97]). Thus, he found that even if Professor Pandy's evidence passed the test of relevance, it engaged the exclusionary opinion rule ('Evidence of an opinion is not admissible to prove the existence of a fact about the existence of which the opinion was expressed': s76) and was not saved by the exception for opinions based on

Significantly too Justice Beale found that the evidence by Professor Pandy

*First, clips 1–36 and 95 show D walking. Second, Professor Pandy's analysis of D's gait in those clips shows that D has a tendency to walk a certain way. Third, because D has such a tendency, he can be expected to walk that way on other occasions. Fourth, clips 37–94 show the shooter walking. Fifth, the way he walks is closely similar to the gait tendency exhibited by D. Taken together, the evidence of D's gait tendency, and its close similarity to the shooter's gait, support P's case that* 

This meant that it engaged the exclusionary rules in s97 of the uniform rules of evidence in Australia, requiring evidence to have significant probative value to be admitted. He found that it did not and therefore it constituted inadmissible ten-

Justice Beale also considered whether the evidence, if it was relevant, which he had found it was not, should be excluded on the basis that its probative value was outweighed by the danger of its constituting evidence that was unfair to the accused. He concluded that the probative value of his evidence was modest because, taken at its highest, it was evidence of similarity, not identity ([16] at [118]). In

*there is no evidence as to how common or uncommon in the general population are the mean step length, step frequency and walking speed of the subjects in the clips. Further, Professor Pandy does not assert that the subjects of the relevant clips are elderly, just that the spatio-temporal gait features are more consistent with the gait* 

Justice Beale identified two ways in which Professor Pandy's evidence had the potential to be misused – by the jury attaching more weight to it than it deserved, especially in light of his using the phrase, 'remarkably similar' and by reason of the jury engaging in tendency reasoning, a risk that he considered 'very real.' This led

Importantly, in 2020 the Chartered Society of Forensic Science and the College of Podiatry [24] published a 'Code of Practice for Forensic Gait Analysis'. It stipulated that the method used for the preliminary assessment in forensic gait analysis

him to exclude the evidence as more prejudicial than probative.

should include assessment of fact such as (but not limited to):

1.distortions of the image inherent in the footage;

**6. The Chartered Society of Forensic Sciences and the College of** 

2.the resolution (sharpness), lighting and frame rate of the footage;

*DOI: http://dx.doi.org/10.5772/intechopen.99491*

specialised knowledge (s 79).

constituted tendency evidence:

dency evidence.

addition:

*D was the shooter ([16] at [103]).*

*of older persons ([16] at [118]).*

**Podiatry Code of Practice**

#### *Guarding the Gait: Evaluating Forensic Gait Analysis Evidence DOI: http://dx.doi.org/10.5772/intechopen.99491*

*Forensic Analysis - Scientific and Medical Techniques and Evidence under the Microscope*

refrained from attributing any specific age estimate to the subjects.

toe-out gait in the community ([16] at [37]).

'comparing apples with apples':

*at [87]).*

the subjects in the two groups of clips were 'remarkably similar' ([16] at [35]). He

He observed that both feet of the subjects exhibited toe-out gait, although he did not make measurements of it. He stated that it appeared greater than normal for healthy young adults but he did not know the prevalence of a greater than normal

Justice Beale declined to admit the evidence of Professor Pandy. He reviewed

the relevance of the evidence by evaluating the potential for a jury to have rationally accepted the reliability of Professor Pandy's calculations. He noted the defects in his evidence about 'rounding-offs' and observed that they may have been concentrated in one group (at [85]) and noted too that Professor Pandy had conceded that the CCTV frame rates, about which he said he knew nothing, may have affected the accuracy of his subjective judgements. He was troubled too that Professor Pandy used the time stamps on the CCTV clip to make his calculations but did not check the accuracy of the various stamps for the various CCTV cameras, as well as the fact that the subjects did not always walk in straight lines between points A and B and that at times there was excessive lateral movement by the subjects. He agreed with the submission from the prosecution that none of these matters may have significantly affected the accuracy of Professor Pandy's calculations but found that 'there is no way of knowing whether that is the case' (at [86]). That led Justice Beale to conclude: 'If the jury is to act rationally, there must be a proper basis for the jury to conclude that the accuracy of his calculations were not significantly affected by these matters. The evidence fails to provide a proper basis for such a conclusion' ([16] at [86]). He was also troubled by what he described as the difficulty of concluding rationally that Professor Pandy was

*He conceded in cross-examination that there was no way of knowing whether the subjects in clips 1–95 were walking at their preferred speed. And yet he based his opinion that the subjects had gait patterns more consistent with older persons primarily on a comparison of the data with results obtained in gait studies of young and old adults whom it was known were walking at their preferred speed ([16]* 

These issues led him to rule that the evidence of Professor Pandy failed the relevance test under s55 of Australia's 'uniform evidence legislation' and this made it inadmissible. The test in this regard was whether it had the potential to rationally affect the existence of a fact in issue between the prosecution and the defence. In addition, Justice Beale was at pains to identify the area of specialised knowledge that the prosecution was seeking to adduce. He concluded that it was 'forensic gait analysis of subjects recorded on CCTV footage', this descriptor ultimately being important. He found that the fact that Professor Pandy conceded he was a novice in relation to the task of comparison – whether any of the subjects were the same – and also the CCTV aspect was significant. Professor Pandy conceded that had never undertaken gait analysis using CCTV recordings ([16] at [94]). Justice Beale found Professor Pandy's failure to discuss dissimilarities of gait to be a significant omission in his evidence and that it called into question his expertise to undertake comparative gait analysis. In addition, Justice Beale emphasised that Professor Pandy had conceded that it was the first time that he had conducted forensic gait comparison of subjects recorded on CCTV footage – 'it is difficult to see how Professor Pandy can be considered an expert in that field when this is the first time he has performed the task. For all his undoubted learning and experience,

**14**

I am not satisfied that Professor Pandy is an expert in the relevant area of FGA ([16] at [97]). Thus, he found that even if Professor Pandy's evidence passed the test of relevance, it engaged the exclusionary opinion rule ('Evidence of an opinion is not admissible to prove the existence of a fact about the existence of which the opinion was expressed': s76) and was not saved by the exception for opinions based on specialised knowledge (s 79).

Significantly too Justice Beale found that the evidence by Professor Pandy constituted tendency evidence:

*First, clips 1–36 and 95 show D walking. Second, Professor Pandy's analysis of D's gait in those clips shows that D has a tendency to walk a certain way. Third, because D has such a tendency, he can be expected to walk that way on other occasions. Fourth, clips 37–94 show the shooter walking. Fifth, the way he walks is closely similar to the gait tendency exhibited by D. Taken together, the evidence of D's gait tendency, and its close similarity to the shooter's gait, support P's case that D was the shooter ([16] at [103]).*

This meant that it engaged the exclusionary rules in s97 of the uniform rules of evidence in Australia, requiring evidence to have significant probative value to be admitted. He found that it did not and therefore it constituted inadmissible tendency evidence.

Justice Beale also considered whether the evidence, if it was relevant, which he had found it was not, should be excluded on the basis that its probative value was outweighed by the danger of its constituting evidence that was unfair to the accused. He concluded that the probative value of his evidence was modest because, taken at its highest, it was evidence of similarity, not identity ([16] at [118]). In addition:

*there is no evidence as to how common or uncommon in the general population are the mean step length, step frequency and walking speed of the subjects in the clips. Further, Professor Pandy does not assert that the subjects of the relevant clips are elderly, just that the spatio-temporal gait features are more consistent with the gait of older persons ([16] at [118]).*

Justice Beale identified two ways in which Professor Pandy's evidence had the potential to be misused – by the jury attaching more weight to it than it deserved, especially in light of his using the phrase, 'remarkably similar' and by reason of the jury engaging in tendency reasoning, a risk that he considered 'very real.' This led him to exclude the evidence as more prejudicial than probative.
