**Abstract**

Novel scientific evidence challenges courts in terms of how they can evaluate reliability for the purposes of making admissibility decisions and assigning probative value to information that is adduced before them. An example of such problematic evidence is forensic gait analysis evidence which is in its infancy as a discipline of forensic science. This chapter reviews how objections to forensic gait analysis evidence have been handled in judicial decisions at first instance and on appeal in Canada, the United Kingdom and Australia. It identifies vulnerabilities in such evidence, especially when jurors are required to incorporate expert opinions (often from podiatrists) about the similarities in gait between that of the accused and a person seen on CCTV footage. The chapter expresses concern about the current scientific basis for such evidence in the absence of well developed databases in relation to gait characteristics, difficulties that characterise interpretation of CCTV footage, and the role that subjective issues can play in analyses by experts in gait interpretation. It notes a United Kingdom initiative in formulating a code of practice for forensic gait analysts but calls for caution in relation to reception and weight to be attached to such evidence until its scientific status becomes more developed.

**Keywords:** Novel scientific evidence, forensic gait analysis evidence, admissibility, probative value, weight, miscarriages of justice

#### **1. Introduction**

Forensic gait analysis is one of a number of novel areas of scientific evidence that have troubled the courts in recent years and led to conflicting curial decisions in relation to admissibility and probative value. In this regard it takes its place alongside facial mapping and body mapping evidence, psychological autopsy evidence, polygraph evidence, lip-reading evidence and ear print comparison evidence [1] as a form of evidence that carries the potential to appear to be more scientifically reliable than it is and therefore which carries a risk of misevaluation if not critically scrutinised. Such evidence is particularly problematic in criminal trials when verdicts are determined by lay jurors. This is because of the danger that decisionmakers will invest overmuch trust in evidence that appears to be scientifically rigorous when it may not be [2].

Forensic gait analysis functions as an example of a dangerous category of apparently scientific evidence that is beguilingly probative but which has the potential to lead to miscarriages of justice. It challenges decision-making by courts and attempts by law reformers to formulate criteria for determining admissibility or at least indicia for safeguards so that misimpressions are not given about evidentiary reliability

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

which may lead to miscarriages of justice. Further, it raises questions about those who are prepared to hold themselves out as forensic experts in the area.

This chapter reviews the current status of knowledge about forensic gait analysis. It identifies significant judicial decisions about the area and it reflects on measures that need to be adopted to minimise the risks that inappropriate reliance will be placed upon problematic application of this form of evidence in criminal trials before it is developed further and acquires the attributes of scientific reliability.

### **2. Forensic gait analysis**

Gait is the way in which a person takes steps when walking or running. It consists of a series of largely repetitive, cyclical movements that are generally symmetrical. It can be observed at a distance, without the knowledge of a person of interest and cannot easily be concealed or dissimulated. Gait analysis has been defined as 'the systematic study of human walking, using the eye and brain of experienced observers, augmented by instrumentation for measuring body movements, body mechanics, and the activity of the muscles' [3–5]. It can be undertaken by observations that a person is bow-legged or has knock-knees or a has a foot that points in or out. It can include consideration of the joints and segments of various parts of the body, including the hips. A variety of tools can be employed to enable calculation of lengths or angles.

Forensic gait analysis is the analysis of the style or manner in which a person walks, as applied to legal issues, including in the context of criminal trials. It has emerged as an important aspect of forensic podiatry, which has been defined as 'the application of sound and researched podiatric knowledge and experience in forensic investigations to show the association of an individual with a scene of crime, or to answer any other legal question concerned with the foot or footwear that requires knowledge of the functioning foot' [6–8]. The area of forensic gait analysis is an evolving and controversial area of scientific controversy [5, 9–12] that generally involves the use of closed circuit television ('CCTV') footage that can be of variable quality in which a comparison is made of a criminal perpetrator's gait with that of the accused. A number of judicial decisions on the issue of admissibility have been handed down, including on appeal in Canada (*R v Aitken*) [13, 14]; the United Kingdom (*Otway v The Queen*) [4], (*Hashi v The Queen*) [15] and Australia (*R v Crupi*) [16].

### **3. Canadian authority**

In *R v Aitken* [13] the accused was charged with murder. There were no witnesses but the fatal shooting outside a Chelsea apartment was captured on the security CCTV positioned above the doorway to a building. Eighteen hours before the shooting CCTV also captured a person of similar size and stature as the shooter apparently canvassing the area and inspecting the buzzer system (the person of interest). The prosecution proposed to call persons whom it proffered as experts from two different but, it maintained, complementary disciplines.

The first expert was Hayden Kelly who held a degree in podiatric medicine and had been practising since 1987 in the United Kingdom. He had seen approximately 38,000 patients. In 2002 he became a podiatric surgeon. From 2006 to the time of the trial in 2008 he had been a researcher in forensic gait analysis identification at Barts College, which is part of the University of London. He had been consulted in approximately 150 legal cases and written over 50 expert opinions. He had testified in the English criminal courts over twenty times.

**5**

of dissimilarity.

1.Relevance;

*Guarding the Gait: Evaluating Forensic Gait Analysis Evidence*

The second expert was Dr. Vernon Brugge who held a doctorate in biology and was held out by the prosecution as an expert in examining photographic evidence. He joined the Federal Bureau of Investigation as a forensic scientist who examined photographic evidence in the technological digital evidence laboratory in Virginia. He had given expert evidence in forensic image analysis, including photographic comparisons, photogrammetry, image and video authentication on some two dozen occasions. He had performed facial and clothing comparisons hundreds to thousands of times. Dr. Brugge's evidence included photogrammetric evidence and facial and clothing comparisons. In his work undertaking photographic comparison, Dr. Brugge compared features on an object or person depicted in a questioned image with a known image to identify or exclude from similarity, utilising 'class characteristics' -those that are common to a group or class of people - and 'individual charac-

teristics' identifying characteristics that separate someone from the class.

1.He views video footage (or stills) of an individual to determine:

b.If there is a particularly distinctive gait or feature of gait shown.

a.If the quality of the film is sufficiently clear, and

to see if the same features or gait exist;

known individual(s) ([13] at [10]).

Mr. Kelly described his forensic gait analysis procedure as having three steps:

2.If he finds distinctive features, then he views other footage of an individual(s)

3.Following that, the analysis is performed on a control, which is footage of a

His view was that the person of interest, the shooter, and the accused shared a "very strong likeness" in that they all had 'very abducted left and right feet and an everted left foot' ([13] at [13]). He expressed the view that he 'would not expect to see this in more than one percent of the population. He did not observe anything in the material with which he was provided that suggested that the accused could not have been the person of interest or the shooter depicted in the videos ([13] at [13]). Thus his testimony amounted to identification of points of similarity and no points

Dr. Brugge used Photoshop techniques and a power point program to enhance and overlay known images on enhanced questioned images to detect similarities and differences. He compared still photographs from the video outside the Chelsea apartment where the murder took place with photographs of the accused. His evidence was he could not identify the accused as the person of interest or the shooter, but he could not exclude him either. Dr. Brugge could find no 'individualizers', such as scars, marks, moles, etc., that could lead to positive identification or exclusion of any of the individuals depicted in the photographs. Similarly, the clothing worn by the person of interest or the shooter bore no individual identifiers such as rips, tears or stains. The defence accepted that Dr. Brugge could testify as to how the video and video stills were processed to improve details by adjusting brightness and contrast

Justice Satanove applied the Canadian tests in relation to expert evidence admissibility set out by the Supreme Court in *R v Mohan* [17], requiring establishment of:

and image enhancement but not the photographic comparisons.

2.Necessity in assisting the trier of fact;

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

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

who are prepared to hold themselves out as forensic experts in the area.

**2. Forensic gait analysis**

calculation of lengths or angles.

**3. Canadian authority**

(*Hashi v The Queen*) [15] and Australia (*R v Crupi*) [16].

different but, it maintained, complementary disciplines.

in the English criminal courts over twenty times.

which may lead to miscarriages of justice. Further, it raises questions about those

This chapter reviews the current status of knowledge about forensic gait analysis. It identifies significant judicial decisions about the area and it reflects on measures that need to be adopted to minimise the risks that inappropriate reliance will be placed upon problematic application of this form of evidence in criminal trials before it is developed further and acquires the attributes of scientific reliability.

Gait is the way in which a person takes steps when walking or running. It consists of a series of largely repetitive, cyclical movements that are generally symmetrical. It can be observed at a distance, without the knowledge of a person of interest and cannot easily be concealed or dissimulated. Gait analysis has been defined as 'the systematic study of human walking, using the eye and brain of experienced observers, augmented by instrumentation for measuring body movements, body mechanics, and the activity of the muscles' [3–5]. It can be undertaken by observations that a person is bow-legged or has knock-knees or a has a foot that points in or out. It can include consideration of the joints and segments of various parts of the body, including the hips. A variety of tools can be employed to enable

Forensic gait analysis is the analysis of the style or manner in which a person walks, as applied to legal issues, including in the context of criminal trials. It has emerged as an important aspect of forensic podiatry, which has been defined as 'the application of sound and researched podiatric knowledge and experience in forensic investigations to show the association of an individual with a scene of crime, or to answer any other legal question concerned with the foot or footwear that requires knowledge of the functioning foot' [6–8]. The area of forensic gait analysis is an evolving and controversial area of scientific controversy [5, 9–12] that generally involves the use of closed circuit television ('CCTV') footage that can be of variable quality in which a comparison is made of a criminal perpetrator's gait with that of the accused. A number of judicial decisions on the issue of admissibility have been handed down, including on appeal in Canada (*R v Aitken*) [13, 14]; the United Kingdom (*Otway v The Queen*) [4],

In *R v Aitken* [13] the accused was charged with murder. There were no witnesses

The first expert was Hayden Kelly who held a degree in podiatric medicine and had been practising since 1987 in the United Kingdom. He had seen approximately 38,000 patients. In 2002 he became a podiatric surgeon. From 2006 to the time of the trial in 2008 he had been a researcher in forensic gait analysis identification at Barts College, which is part of the University of London. He had been consulted in approximately 150 legal cases and written over 50 expert opinions. He had testified

but the fatal shooting outside a Chelsea apartment was captured on the security CCTV positioned above the doorway to a building. Eighteen hours before the shooting CCTV also captured a person of similar size and stature as the shooter apparently canvassing the area and inspecting the buzzer system (the person of interest). The prosecution proposed to call persons whom it proffered as experts from two

**4**

The second expert was Dr. Vernon Brugge who held a doctorate in biology and was held out by the prosecution as an expert in examining photographic evidence. He joined the Federal Bureau of Investigation as a forensic scientist who examined photographic evidence in the technological digital evidence laboratory in Virginia. He had given expert evidence in forensic image analysis, including photographic comparisons, photogrammetry, image and video authentication on some two dozen occasions. He had performed facial and clothing comparisons hundreds to thousands of times. Dr. Brugge's evidence included photogrammetric evidence and facial and clothing comparisons. In his work undertaking photographic comparison, Dr. Brugge compared features on an object or person depicted in a questioned image with a known image to identify or exclude from similarity, utilising 'class characteristics' -those that are common to a group or class of people - and 'individual characteristics' identifying characteristics that separate someone from the class.

Mr. Kelly described his forensic gait analysis procedure as having three steps:

	- a.If the quality of the film is sufficiently clear, and
	- b.If there is a particularly distinctive gait or feature of gait shown.

His view was that the person of interest, the shooter, and the accused shared a "very strong likeness" in that they all had 'very abducted left and right feet and an everted left foot' ([13] at [13]). He expressed the view that he 'would not expect to see this in more than one percent of the population. He did not observe anything in the material with which he was provided that suggested that the accused could not have been the person of interest or the shooter depicted in the videos ([13] at [13]). Thus his testimony amounted to identification of points of similarity and no points of dissimilarity.

Dr. Brugge used Photoshop techniques and a power point program to enhance and overlay known images on enhanced questioned images to detect similarities and differences. He compared still photographs from the video outside the Chelsea apartment where the murder took place with photographs of the accused. His evidence was he could not identify the accused as the person of interest or the shooter, but he could not exclude him either. Dr. Brugge could find no 'individualizers', such as scars, marks, moles, etc., that could lead to positive identification or exclusion of any of the individuals depicted in the photographs. Similarly, the clothing worn by the person of interest or the shooter bore no individual identifiers such as rips, tears or stains. The defence accepted that Dr. Brugge could testify as to how the video and video stills were processed to improve details by adjusting brightness and contrast and image enhancement but not the photographic comparisons.

Justice Satanove applied the Canadian tests in relation to expert evidence admissibility set out by the Supreme Court in *R v Mohan* [17], requiring establishment of:

#### 1.Relevance;

2.Necessity in assisting the trier of fact;

3.The absence of any exclusionary rule; and.

#### 4.A properly qualified expert.

She found the evidence of Mr. Kelly to have 'high probative value' in that it tended to establish a fact in issue, the identity of the killer ([13] at [19]). However, she concluded that Dr. Brugge's evidence was not admissible although she permitted his evidence on the technological enhancements he made to the videos and stills that were shown to the jury.

Justice Satanove accepted that: 'Evidence that is otherwise logically relevant may be excluded if its probative value is overborne by its prejudicial effect; if it involves an inordinate amount of time that is not commensurate with its value; or if it is misleading in the sense that its effect on the trier of facts, particularly a jury, is out of proportion to its reliability. There is a danger that expert evidence will be misused and will distort the fact-finding process. Dressed up in scientific language that the jury does not easily understand, and submitted through a witness of impressive credentials, the evidence may lie be accepted by the jury as being virtually infallible and, thus, given more weight than it deserves' ([13] at [19]). She observed that the potentially prejudicial effect of the experts' evidence may in their impressive credentials and their aura of infallibility ([13] at [19]).

Tellingly, she noted that Mr. Kelly drew a conclusion as to the degree of prevalence of gait characteristics in the general population 'that appears significant, yet lacks a scientific basis' ([13] at [23]). To address this risk, she allowed Mr. Kelly's evidence but not his opinion about the extent of abduction and eversion in the general population. However, Justice Satanove was not satisfied that Dr. Brugge's evidence was 'necessary', as that term is understood under Canadian law, namely that such evidence is outside the experience and knowledge of a judge or jury. She accepted that it may be '"helpful" as an experienced person's observation of facial features and clothing, but the jury will be able to form their own conclusions without this help. In my opinion, Dr. Vorder Brugge's comparison evidence does not offer any information outside of the purview of the ordinary jury, and therefore does not meet the test of necessity' ([13] at [24]).

She was not satisfied that the evidence of Mr. Kelly constituted "novel science": "podiatry has been in existence for a thousand years and the expertise of a podiatrist to analyze an individual's gait has long been accepted and practiced in a clinical setting. After carefully viewing the video frame by frame, many, many times, with his trained and practiced eye, he is able to point out fairly unique characteristics of the gait and stance of the individuals depicted in the video. The features are akin to individual identifiers to some extent. I do not think there is a danger of the jury being mesmerized by what is quite simply an exercise of expertise in observation and diagnosis" ([13] at [34]). The result was that Justice Satanove admitted the gait analysis evidence of Mr. Kelly, save the part which referred to a mathematically expressed degree of prevalence but excluded the evidence of Dr. Brugge insofar as it related to technological enhancements he made to videos and stills, but excluded his comparison evidence.

Cunliffe and Edmond [10] have criticised the ruling by Justice Satanove as an 'admissibility compromise. However, on appeal (*R v Aitken* [14]) the British Columbia Court of Appeal [14] upheld the decision at first instance to admit the evidence of Dr. Kelly. The Court applied the *Mohan* test formulated by the court in *R v Abbey* [18] at [80] where it was held that a trial judge must conduct a 'rulebased' analysis to assess compliance with preconditions to admissibility:

• the proposed opinion must relate to a subject matter that is properly the subject of expert opinion evidence;

**7**

before the Court.

probative value.

*Guarding the Gait: Evaluating Forensic Gait Analysis Evidence*

• the witness must be qualified to give the opinion;

entirely from the expert opinion rule; and

• the proposed opinion must not run afoul of any exclusionary rule apart

The Court of Appeal agreed with Justice Satanove that the evidence of Mr. Kelly was not 'novel' for the purposes of the *Mohan* test and concluded that his evidence fell into the category of 'specialized knowledge gained through experience and specialized training' ([14] at [80]). It held that this meant that there was no error in the trial judge failing to consider indicia of scientific validity such as peer review, rate of error and adherence to a scientific method – 'These factors have limited relevance in a case like the one at hand where a witness's expertise is gained over a period of years through observation and experience in the professional realm' ([14] at [80]). The Court of Appeal concluded that Mr. Kelly's evidence that there was a 'very strong likeness' in gait between the individuals shown on the video footage was 'merely a distillation of his factual observations, and that he did not usurp the role of the trier of fact by offering a conclusion on the ultimate issue of the identity of the shooter' ([14] at [84]). This meant that he was not breaching the preclusion on giving evidence on an ultimate issue but simply offering a piece of circumstantial evidence that narrowed the gap between who could be the shooter and the person of

In important respects, the most contentious aspect of the Court of Appeal's judgement was its endorsement in the context of forensic gait analysis ([14] at [85])

*... I doubt that the jury would have difficulty critically evaluating [the expert's] opinion. There was nothing complex or obscure about his methodology, the material he relied on in forming his opinion or the language in which he framed and explained his opinion. As when measuring the benefits flowing from the admission of expert evidence, the trial judge as "gatekeeper" must go beyond truisms about the risks inherent in expert evidence and come to grips with those risks as they apply to* 

The Court of Appeal found no error in the evidence of Mr. Kelly being placed before the jury to provide assistance in their evaluation of the images so that the jurors might utilise the knowledge acquired by Mr. Kelly through his training and experience in arriving at their own conclusions regarding the identity of the shooter ([14] at [86]). The Court of Appeal reviewed English decisions on the issue, including that of *Otway v The Queen* [6] (see below), which had been decided since the trial judge's decision, and classified them to be of persuasive authority and supportive of the admissibility of forensic gait analysis in the circumstances of what was

While Cunliffe and Edmond [10] have been critical of the latitude extended by the trial and appellate decisions as to the admissibility of forensic gait analysis in the *Aitken* judgements, it is apparent that at both levels the courts regarded the evidence as having probative value which the jury was in an adequate position to evaluate. Therein lies the contentious and problematic aspects of the judgements in that the jurors had no statistical tool on the basis of which to evaluate the significance of the points of similarity identified by the expert and there was a risk of their attributing weight and giving deference to the evidence which was out of proportion to its

of the comments of Justice of Appeal Doherty in *Abbey* ([18] at [92]):

*the particular circumstances of the individual case.*

• the proposed opinion must be logically relevant to a material issue.

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

interest and the accused.

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

She found the evidence of Mr. Kelly to have 'high probative value' in that it tended to establish a fact in issue, the identity of the killer ([13] at [19]). However, she concluded that Dr. Brugge's evidence was not admissible although she permitted his evidence on the technological enhancements he made to the videos and stills

Justice Satanove accepted that: 'Evidence that is otherwise logically relevant may be excluded if its probative value is overborne by its prejudicial effect; if it involves an inordinate amount of time that is not commensurate with its value; or if it is misleading in the sense that its effect on the trier of facts, particularly a jury, is out of proportion to its reliability. There is a danger that expert evidence will be misused and will distort the fact-finding process. Dressed up in scientific language that the jury does not easily understand, and submitted through a witness of impressive credentials, the evidence may lie be accepted by the jury as being virtually infallible and, thus, given more weight than it deserves' ([13] at [19]). She observed that the potentially prejudicial effect of the experts' evidence may in their impressive

Tellingly, she noted that Mr. Kelly drew a conclusion as to the degree of prevalence of gait characteristics in the general population 'that appears significant, yet lacks a scientific basis' ([13] at [23]). To address this risk, she allowed Mr. Kelly's evidence but not his opinion about the extent of abduction and eversion in the general population. However, Justice Satanove was not satisfied that Dr. Brugge's evidence was 'necessary', as that term is understood under Canadian law, namely that such evidence is outside the experience and knowledge of a judge or jury. She accepted that it may be '"helpful" as an experienced person's observation of facial features and clothing, but the jury will be able to form their own conclusions without this help. In my opinion, Dr. Vorder Brugge's comparison evidence does not offer any information outside of the purview of the ordinary jury, and therefore does not meet the test of

She was not satisfied that the evidence of Mr. Kelly constituted "novel science": "podiatry has been in existence for a thousand years and the expertise of a podiatrist to analyze an individual's gait has long been accepted and practiced in a clinical setting. After carefully viewing the video frame by frame, many, many times, with his trained and practiced eye, he is able to point out fairly unique characteristics of the gait and stance of the individuals depicted in the video. The features are akin to individual identifiers to some extent. I do not think there is a danger of the jury being mesmerized by what is quite simply an exercise of expertise in observation and diagnosis" ([13] at [34]). The result was that Justice Satanove admitted the gait analysis evidence of Mr. Kelly, save the part which referred to a mathematically expressed degree of prevalence but excluded the evidence of Dr. Brugge insofar as it related to technological enhance-

ments he made to videos and stills, but excluded his comparison evidence.

based' analysis to assess compliance with preconditions to admissibility:

Cunliffe and Edmond [10] have criticised the ruling by Justice Satanove as an 'admissibility compromise. However, on appeal (*R v Aitken* [14]) the British Columbia Court of Appeal [14] upheld the decision at first instance to admit the evidence of Dr. Kelly. The Court applied the *Mohan* test formulated by the court in *R v Abbey* [18] at [80] where it was held that a trial judge must conduct a 'rule-

• the proposed opinion must relate to a subject matter that is properly the subject

3.The absence of any exclusionary rule; and.

credentials and their aura of infallibility ([13] at [19]).

4.A properly qualified expert.

that were shown to the jury.

necessity' ([13] at [24]).

of expert opinion evidence;

**6**


The Court of Appeal agreed with Justice Satanove that the evidence of Mr. Kelly was not 'novel' for the purposes of the *Mohan* test and concluded that his evidence fell into the category of 'specialized knowledge gained through experience and specialized training' ([14] at [80]). It held that this meant that there was no error in the trial judge failing to consider indicia of scientific validity such as peer review, rate of error and adherence to a scientific method – 'These factors have limited relevance in a case like the one at hand where a witness's expertise is gained over a period of years through observation and experience in the professional realm' ([14] at [80]). The Court of Appeal concluded that Mr. Kelly's evidence that there was a 'very strong likeness' in gait between the individuals shown on the video footage was 'merely a distillation of his factual observations, and that he did not usurp the role of the trier of fact by offering a conclusion on the ultimate issue of the identity of the shooter' ([14] at [84]). This meant that he was not breaching the preclusion on giving evidence on an ultimate issue but simply offering a piece of circumstantial evidence that narrowed the gap between who could be the shooter and the person of interest and the accused.

In important respects, the most contentious aspect of the Court of Appeal's judgement was its endorsement in the context of forensic gait analysis ([14] at [85]) of the comments of Justice of Appeal Doherty in *Abbey* ([18] at [92]):

*... I doubt that the jury would have difficulty critically evaluating [the expert's] opinion. There was nothing complex or obscure about his methodology, the material he relied on in forming his opinion or the language in which he framed and explained his opinion. As when measuring the benefits flowing from the admission of expert evidence, the trial judge as "gatekeeper" must go beyond truisms about the risks inherent in expert evidence and come to grips with those risks as they apply to the particular circumstances of the individual case.*

The Court of Appeal found no error in the evidence of Mr. Kelly being placed before the jury to provide assistance in their evaluation of the images so that the jurors might utilise the knowledge acquired by Mr. Kelly through his training and experience in arriving at their own conclusions regarding the identity of the shooter ([14] at [86]). The Court of Appeal reviewed English decisions on the issue, including that of *Otway v The Queen* [6] (see below), which had been decided since the trial judge's decision, and classified them to be of persuasive authority and supportive of the admissibility of forensic gait analysis in the circumstances of what was before the Court.

While Cunliffe and Edmond [10] have been critical of the latitude extended by the trial and appellate decisions as to the admissibility of forensic gait analysis in the *Aitken* judgements, it is apparent that at both levels the courts regarded the evidence as having probative value which the jury was in an adequate position to evaluate. Therein lies the contentious and problematic aspects of the judgements in that the jurors had no statistical tool on the basis of which to evaluate the significance of the points of similarity identified by the expert and there was a risk of their attributing weight and giving deference to the evidence which was out of proportion to its probative value.
