(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.
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