Guest Post — Gait Analysis and the Evidence Act

(This is a guest post by Pratyush Singh)

Gait analysis is a methodical examination of the walk of a human being with the use of trained observers, which may also be supplemented with equipment that measures muscle activation, body motions, and body mechanics. On 02.06.2022, in State of Maharashtra v. Mohan Kathwaru Chauhan [SC/ST Spl Case No. 380 of 2021] the Sessions Court of Dinoshi, Mumbai sentenced the accused to death for the charges of rape and murder [the case is now before the Bombay High Court for confirmation]. 

In this case, the prosecution relied on the ‘gait analysis test’ as one of the corroborating pieces of evidence to identify the accused. While there has been praise in the media for usage of this ‘novel method,’ there has been no attempt to critically examine its scientific merits.

It is in this broad context that this post argues that the gait analysis test should not be utilised by the Indian Courts due to limitations that it comes with. To that end, we will first go over the existing jurisprudence around gait pattern recognition in India, second, go over the weaknesses of such an application, and third, analyse its usage and criticisms in other jurisdictions to suggest a way forward for the Indian Courts. 

Tracing the Indian Jurisprudence 

Recognition of gait by acquaintances 

With respect to ordinary witnesses, the criminal jurisprudence in India has evolved to allow identification based on the gait of the accused person under specified circumstances. In Pruthiviraj Jayantibhai Vanol v. Dinesh Dayabhai Vala (2021), the Supreme Court stated that an accused can be identified by their gait even at night provided that the witness is well acquainted with the accused. The ‘well acquainted’ component of the test can be better understood through cases. 

In Kirpal Singh v. State Of Uttar Pradesh (1963), the Supreme Court noted that since the witness had met the accused several times within a fortnight, they could be said to be familiar with each other. While on the other hand, in Rai Singh v. State of Himachal Pradesh (2000, Himachal Pradesh), the identification by recognising the gait of the accused was rejected on the ground that the prosecution witness had only seen the accused on two occasions which was also a year before the occurrence of the crime. 

It must be kept in mind that such recognition of the gait of a person is not the sole piece of evidence that the courts rely upon. In Saha Alam Miah v. State of Tripura (2014), the Tripura High Court with regards to  identification of an accused by the timbre of their gait, stated that such identification cannot be solely relied upon and “[t]he courts usually require further corroboration to return the finding of conviction.” These other means of corroboration may include the body shape of the accused, their clothes and even their voice. 

Expert Opinion on Gait Analysis

Gait based recognition has also been used in test identification parades and by special investigation teams in criminal matters. However, in the instances that I came across by searching legal databases (SCC Online and Casemine) it seems all of these have focused on gait recognition by ordinary witnesses and not a full-fledged analysis was undertaken by an expert. The only case which comes close to such an exercise is Vivekanand Bihari v. State (2018, Delhi). In this case, a private organisation conducted a gait pattern analysis based on closed-circuit television (“CCTV”) footage. However, this evidence was not considered by the court owing to the possibility of tampering that had arisen during the chain of custody.

This brings us to the case of Mohan Chauhan, with which we began. In this case, a chemical analyst (“the expert”) from the Directorate of Forensic Science Laboratories (FSL) Mumbai conducted a gait test on the accused. The expert explained the test to the Court as “compar[ing] the movement of the suspect and the sample video.” The accused was asked to walk in a recreated scene in front of the panchas, the police and experts who were recording the entire process. This video that was later compared to the CCTV recording by the expert. During cross-examination, the expert revealed that the walking style of the accused and the person captured by the CCTV cameras were “similar” and not “same”. They also revealed that discomfort due to footwear, injuries or even facing trauma can affect their walking style and so it is nearly impossible to get a 100% match on comparison. 

Even though the judge acknowledged that there was no precedent for such a test being conducted by an expert, the court ended up ruling that such a fact would not stop the court from considering the said test. 

Did the Court in Mohan Chauhan get it right?

Section 45 of the Indian Evidence Act 1872 (“IEA”) talks about expert evidence. In Ramesh Chandra Agrawal v. Regency Hospital Limited (2009), the Supreme Court observed that an expert is a person having specialised knowledge who takes up an advisory role during the proceedings of the court for matters “outside the knowledge and experience of the lay person.” It further stated that whenever such an expert gives any opinion regarding a fact, it needs to be backed by adequate data, otherwise even if the evidence is admissible, it would not be considered while adjudicating the matter. 

With respect to the first requirement, Mohan Chauhan accepted the testimony of a chemical analyst as the expert for gait analysis. Chemical analysts unlike podiatrists (people specialize in matters pertaining to the feet) cannot be said to be ‘experts’ in gait analysis as they primarily specialize in dealing with chemical substances. In State of Himachal Pradesh v. Jai Lal (1999, SC), the qualifications of the expert were heavily discussed. The expert’s lack of experience in the matter at hand and the lack of data he had presented was used to entirely discard his testimony. No such analysis was done by the court in Mohan Chauhan which could have entirely determined the usage of the gait analysis for the case.

Second, in Mohan Chauhan, the expert stated that no two people can have the same gait pattern. This statement however is not backed by data. Most academic papers that make claims related to uniqueness of gait cite either Murray or Winter. However, these papers have not pointed to any substantial study either and hence remain an “unproven conjecture.” 

Moreover, there are two substantial problems with assuming uniqueness of gait in a comparative CCTV analysis. Firstly, even if we assume that gait patterns can be unique, uniqueness can only be determined by precise measurements which are simply not possible with available quality of CCTV footage received. Secondly, as noted by the expert in Mohan Chauhan, multitudes of factors can influence the gait of a person like footwear or injuries. The list does not here; it has been proven that factors such as walking speed, walking surfaces, crowded spaces and even whether or not the person was using their mobile phones can influence their gait. Both these concerns are also shared by the Royal Society of Edinburgh in a 2017 report wherein it concluded saying that “[t]here is no evidence to support the assertion that gait is unique within current or foreseeable limitations of measurements used in forensic gait analysis.” 

It is also worthwhile to note that other evidence such as DNA or fingerprints for which an expert is required cannot be manipulated by an accused. However, during collection of a gait sample, the accused can simply tweak their walk which during the analysis would demonstrate that they are not similar to the person caught in a CCTV footage. These problems are not encountered when a close acquaintance/relative identifies the gait of an accused at the scene of the crime, which is what the earlier line of cases dealt with. 

The author is not disputing the science behind clinical gait analysis. However, the accuracy of something gathered in a controlled setting cannot be superimposed on a comparator of a CCTV footage.

Approaches of Different Jurisdictions 

Canada

R v. Aitken (2012, British Columbia) involved a murder case in a building with no eyewitnesses. However, CCTV right outside the building was able to capture a man similar to the accused scouting the area some hours before the crime. The podiatrist is this case stated that the way the accused’s feet moved in relation to the middle part of the body was the same as that of the person in the footage. This testimony was challenged by the accused on grounds that podiatry is “novel science”, i.e., it is the first time that it was presented to Canadian Courts and is not an accepted practice (much like the objection in Mohan Chauhan). However, the judge noted that podiatry as a scientific study has existed for over thousand years and the only difference is that it is now being applied as “forensic gait analysis”. The evidence was accepted due to its probative value.

This approach by Canadian Courts has been criticised for reaching conclusions without the requisite data . Based on the information we have, we can only conclude that person A has a similar gait to person B. However, there is no data as to the number or frequency of people possessing a similar gait and hence any conclusion reached can be conjecture at best. Another criticism of this test is that the focus has mainly been on qualifications of the expert and an array of technical problems like image quality and frame rates have been ignored. There needs to be a conclusive study to determine how much other factors such as the image quality, percentage of the body shown, and the duration of movement recorded would impact gait analysis.

Australia

Australia has had a starkly different jurisprudence regarding gait analysis when compared to Canada. In  Queen v. Vincenzo Crupi (2020, Victoria), instead of a podiatrist, an expert in mechanical and biomedical engineering was appointed to review over 90 clips of CCTV footage in order to “identify and document any physical characteristics observed in the video clips.” In this case, owing to factors such as low frame rates and data sets, Justice Beale held the expert’s evidence inadmissible. He further stated that the jury should have a proper basis to decide the matter. Since the expert was unable to point to any actual comparative value and lacked adequate expertise in the field, their testimony would be treated as opinion evidence and not an opinion based on specialised knowledge. Justice Beale also clarified that even if the opinion was given by an expert, the testimony still deals with evidence of similarities and not identification. Moreover, the problem of the lack of data on gait available for the general population does not lend high probative value to evidence to such evidence even in its best case.

Can gait analysis be used in the future?

In Arshad v. State of Andhra Pradesh (1995, Andhra Pradesh), it was acknowledged that there are two components of expert evidence, i.e., data evidence and opinion evidence. It was further stated that data evidence cannot be disregarded if it contradicts oral testimony; nevertheless, opinion evidence is merely an interpretation taken from the data and cannot supersede direct eyewitness testimony unless, of course, the discrepancy between the two is so vast as to falsify the testimony. Since unlike in the UK, India does not have a database for gait patterns, it is difficult to put forth any kind of data while presenting evidence. For this reason, and all the other concerns put forth by academics and Justice Beale in Queen v. Crupi, gait analysis in its current state should not be used as scientific evidence. 

So, what can be done? Currently, a black-box study is a good tool for demonstrating the legitimacy of gait analysis used in judicial processes. In this study, two sets of video footage that are typically utilised in court hearings would be given to a variety of practitioners. Some might belong to the same person, while others would belong to different people. The results could then be used to calculate the success/failure rate of the exercise. There has not been any significant, black-box forensic gait analysis research published. The only research that even remotely resembles this design is by Birch and his team in 2013, in which seven “experienced analysts” were instructed to identify one person from five suspects using comparative gait analysis. The rate of failure recognized in this project was around 29%, indicating that only 71% of the tests correctly resulted in identifying the culprit.

Till the time such an exercise is undertaken, Indian Courts should refrain from utilising such evidence, albeit only for corroboration. 

Conclusion

New developments in forensic science will always have an impact on the law. While gait analysis is a recent and exciting area that should be explored, it is simply at a very nascent stage to be accurately utilised by the courts. There is a need to develop a respectable database of gait patterns, along with advancements in analysing the footage gathered from the CCTV cameras before a wide-scale use of such a technique. The purpose of this post was not to criticise the science behind gait analysis but only to caution against its usage without acknowledging its limitations. 

Guest Post: Expert Testimony and Section 293 CrPC, A Critique

(This is a guest post by Bharat Harne)

Expert testimony has come to play an essential role in criminal trials. With the rapid advance in science, courts in India (and across the world) have increasingly started relying on scientific proof and analysis for fact-finding. Since an avowed purpose of a criminal trial is fact-accuracy, scientific evidence is seen as a reliable way to get to the truth of the matter. The opinion of an expert is not binding but is material that helps a court to come to a conclusion about facts that it could not have ascertained on its own. Unlike predominant literature on expert testimony in the Indian context which mostly focuses on its probative value, this post looks at procedural issues surrounding expert testimony. First, I make a distinction between two different kinds of experts i.e., medical experts and non-medical experts who play a role in the criminal justice process. Then, I focus on non-medical experts and evaluate whether the relevant legal provisions ensure fair trial of the accused. 

Types of Experts 

For the purpose of this post, experts can be divided into two types, viz. medical experts and non-medical experts. The terms medical experts will be used to refer to doctors (both government doctors and private practitioners) who prepare reports like a post-mortem report, MLC report etc. 

Medical experts are usually called as prosecution witnesses. Usually, in a criminal investigation, medical experts prepare ‘reports’ which are then used for further investigation and are admitted as ‘documentary evidence’ in a criminal trial. For example, in murder cases, the doctor who does the post-mortem prepares a post-mortem certificate which becomes extremely important in the trial to establish the cause of death. Such medical expert prepares a report which contains information about injury (if any) and can be useful to prove the cause of death, nature of injuries, etc. When the prosecution calls an expert on the stand, they are supposed to prove the contents of their reports because these reports are private documents under the provisions of Indian Evidence Act, 1872. The defense is entitled to cross-examine the expert as to the contents of their report.

The term non-medical experts will refer to various other kinds of experts who play a crucial role in an investigation, such as ballistics expert, serologist, chemical examiner, handwriting expert, fingerprint expert, etc. The justification of this distinction is that the procedural law in India itself treats these experts differently. While, on the one hand, prosecution calls medical experts to prove their opinions/reports, the CrPC exempts the prosecution from calling non-medical experts. 

Section 293 and Non-Medical Experts

S.293 of the Criminal Procedure Code 1973 states that any document purporting to be a report under the hand of a Government scientific expert to whom the section applies may be used as evidence in any inquiry, trial, or other proceedings. In other words, this provision creates an exception to the rule that the contents of a document must be proved. As per s.293(4), the exception only applies to reports prepared under the hand of the following Government scientific experts- any Chemical Examiner or Assistant Chemical Examiner to Government; Chief Controller of Explosives; Director of Finger Print Bureau, Director of Haffkeine Institute Bombay; Director, Deputy Director or Assistant Director of Central Forensic Science Laboratory or a State Forensic Science Laboratory; Serologist to the Government or any such expert notified by the Central Government. To date, the Central Government has not exercised its power to notify any other expert who would be exempt from appearing before a trial court. 

The 41st Report of the Law Commission of India sheds light on the rationale of this exception. It notes that s. 509 of the erstwhile 1898 Code exempted a civil surgeon or other medical witnesses from appearing in a Court of Session if the witness has given evidence in the committing court and his recorded statement is made a part of the evidence by a special rule. The Commission had received a suggestion that even the requirement of appearance before committing court should be done away with, and the report itself should be treated as evidence. However, the Commission observed that such a rule would not be helpful as there is a serious risk of experts becoming ‘irresponsible’ and a trial court, in most cases, would end up summoning the medical expert anyway. Further, Section 510 of the old Code was similar to Section 293 of the CrPC 1973. It exempted certain government experts from proving their reports. The Commission noted that the provision is meant to exempt those experts who, because of their ‘small number’ require ‘special treatment.’ Thus, the primary reason why certain experts are exempted is that they are very few in number, and it would be simply impossible to call them in each and every case. 

It is interesting that the Commission did not consider a possibility that ‘special’ experts might not give reliable evidence. Contrast this with how the Commission rejected giving the same exemption to medical experts. The only reasonable explanation for this differential treatment seems to be that medical experts (usually Government doctors) were more in number than experts who were given the exemption. Moreover, literature on scientific evidence suggests that when forensic labs work under the umbrella of law enforcement/government, the experts in the lab begin to see themselves as law enforcement professionals rather than scientists. Cognitive scientists argue that a close working relationship with law enforcement agencies leads to the subconscious adoption of the role of the prosecutor by scientists. This bias can affect the results of scientific inquiry, which are presented as neutral but, in fact, are biased against the defense. The risk is not of gross misconduct, rather that of subtle unconscious bias. CrPC gives exemption to precisely the agencies (such as Central and State Forensic Science Laboratories) who work very closely with prosecution/law enforcement and are therefore susceptible to bias. This phenomenon has been described in vivid detail for the Indian context by Prof. Lokaneeta in The Truth Machines recently.

An example of such bias was seen in reports of the SBI Laboratory in North Carolina in the United States. After a conviction was overturned after fourteen years because of a dubious report by scientists in SBI Crime Lab, an audit of procedures and standards followed in the lab was ordered. This audit led to startling revelations about the practices in the lab that favored the prosecution. The audit highlighted the fact that for a period of sixteen years, it was the practice of the lab to either withhold or misrepresent information that might benefit the defense in criminal charges. There is no empirical evidence to suggest that Forensic Laboratories in India follow similar pro-prosecution protocols. However, neither scholars nor policymakers have really explored this question, and therefore just because there is no evidence to suggest pro-prosecution bias, it cannot be said that it does not exist. 

Procedural safeguards against bias in Scientific Evidence

It is in this context of bias in forensic evidence that the criminal procedure becomes extremely important. If a forensic scientist is called and put on the stand to prove his report, he will be subject to cross-examination by the defense counsel. It has been argued that questioning an expert about his report is likely to bring out biases within such reports. Of course, it is true that such questioning requires a high level of expertise on the part of defense lawyers and judges. But the fact remains that cross-examination provides the basic minimum safeguard against bias in expert evidence. 

Section 293(2) of CrPC states that the court ‘may, if it thinks fit, summon and examine any such expert as to the subject-matter of his report’. This essentially means that it is up to the discretion of the court to summon the expert. However, the defense can also file an application under s. 293(2) to summon the expert for cross-examination. If the defense does not summon the expert for cross-examination during trial, then it cannot be argued at the appellate level that the expert was not examined. In other words, the burden shifts on the defense to file an application before the trial court to summon the expert. While it may seem that, this works as a safeguard, it would be wrong, in my opinion, to assume that litigants are actually using this safeguard. It is difficult to empirically determine how many applications under s.293(2) are filed and how many of them are allowed. However, there is some evidence to suggest that cross examination under s.293(2) is not as common as one might assume. In Abid Beig v. State of Rajasthan, the Rajasthan HC was dealing with a Narcotics Drugs and Psychotropic Substances Act (NDPS) case wherein the accused had not been given an opportunity to cross-examine the report prepared by scientists of the Forensic Science Laboratory (FSL). The court observed that although the reports of FSL are relevant and admissible by virtue of exception under s. 293, it does not mean that the accused should be denied the right to cross-examine the expert. However, more importantly, the court observed that in ‘large number’ of cases at trial court level, the prosecution reports of FSL are pointed out to the accused only at the time of recording of this statement under s. 313 of CrPC. In other words, after the conclusion examination in chief, so that the defense does not get an opportunity to cross-examine. Further, this issue should be seen in the light of the rationale for exception under s. 293, namely, the ‘small’ number of experts. It is no secret that even now, FSLs are grossly understaffed and the Forensic scientists are overworked. Therefore, going to a court to testify is a hassle and it is possible that the scientists might ask the prosecution to make sure that they are not summoned. Worryingly, the Supreme Court itself Thana Singh v. Central Bureau of Narcotics noted that since a large number cases under NDPS are pending, trial courts should take the ‘benefit’ of Section 293, thereby implying that cross-examination of experts can be dispensed with for ensuring speedy trial. While it is not my contention that speedy trial is not important, it cannot come at the cost of the right to cross-examine. 

It is interesting to contrast India’s position with the United States (US). The Sixth Amendment to the US Constitution gives the right to an accused to be confronted by the witness against him in a criminal trial (what is referred to as the ‘Confrontation’ clause). In Luis E. Melendez-Diaz v. Massachusetts, a case before the US Supreme Court (USSC), the petitioner was alleged to have been trading in cocaine. Some samples were taken and sent to a laboratory for testing. A report was prepared, which confirmed that the samples were, in fact, cocaine. In the trial, the said report was taken as evidence without giving an opportunity to cross-examine the author of the report. The USSC held this to be a violation of the accused’s Sixth Amendment right. More importantly, it acknowledged that forensic reports are not ‘neutral’ as it is widely believed and acknowledged that people working in these labs are often pro-prosecution because of close working relationships with law enforcement.

Way Forward

First of all, the policymakers should rethink the exception provided under section 293. The exception was provided in the Code because these experts were very ‘few’ in number and not because their expertise was not subject to errors/bias. However, doing away with the exception might further burden the already overworked Forensic labs in India. The unfortunate fact is that even now, forensic labs in India are disproportionately low and grossly understaffed. Recently, the Karnataka High Court highlighted the fact that a lot of cases are pending because of delays occurring in Forensic Science Laboratories. This tells us that the exception under section 293, which was supposed to expedite cases, is not working, and policymakers should instead focus on increasing Forensic Laboratories and hiring more experts. Therefore, to save the time of forensic experts, along with increasing Forensic Science infrastructure, policymakers should also focus on video conferencing of expert testimony. A recent study by PGIMER Hospital found that their doctors had saved nearly 30,000 working hours and around Rs. 2.79 crore in the last four years by using a tele-evidence facility. This facility was touted as the first such facility in what was supposed to be a nationwide program undertaken by the Ministry of Health and Family Welfare to install tele-evidence facilities across hospitals and courts in the whole country. However, so far, there has been no update on the status of the implementation of this program. 

Conclusion

Expert testimony plays a crucial role in the endeavour of criminal trials to get to the truth. Advances in medical science in general and forensic science have allowed scientists to answer complicated questions which could not have been answered before. The Indian legal framework adopts a slightly paradoxical approach to the summoning of expert witnesses. Under the Indian Evidence Act the prosecution is obligated to prove the reports of medical experts by getting them to testify before the court orally. While medical experts are obligated to prove the contents of their reports, some ‘special’ experts under the CrPC are exempt from having to come physically to court and take the stand. This exemption is premised not on the scientific objectivity of their expertise but practical problems which the legislature imagined such experts could face in having to travel to court. However, the fact remains that forensic science is not ‘neutral’ and is given to bias, and in failing to consider this issue I argue that the legislature committed a misstep. The practical concerns germane to 1973 can be addressed with relative ease in 2021, using videoconferencing for example. Given the importance of these witnesses to trials and the fact that, ultimately, it’s a matter of personal liberty, the default procedure must be that they appear and testify and are subject to cross-examination – not the present elective approach which places defendants under an onerous burden.