In this case, the officer said that the hairline, forehead and shoulders “were found similar” with the man in the reference photographs, which featured Chauhan.In a first in Mumbai, gait analysis report was among the evidence relied upon by a court hearing a case against a 44-year-old man, accused of raping and murdering a woman in Saki Naka last year.
Mohan Chauhan was convicted and sentenced to death by a special court in Dindoshi on Thursday. The Mumbai Police, in its investigation, had included a forensic report relying on gait analysis to corroborate that the man captured in the CCTV camera footage recovered from the spot of the incident was indeed Chauhan.
The 31st witness in the case was a scientific officer from the state Forensic Sciences Laboratory in Kalina, who had analysed Chauhan’s gait recorded after his arrest and compared it with the CCTV footage seized during investigation.
Explaining gait analysis, the officer deposed that it is a process where the gait of a person – manner of walking – is compared with CCTV camera footage in which the suspect is seen walking.
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The officer explained that a sample video is made of the suspect walking. It requires the same angle, same light conditions and same distance to be covered as in the CCTV footage for the analysis. The sample video and the CCTV footage are compared through a software by static images from both and analysed frame by frame.
In this case, the officer said that the hairline, forehead and shoulders “were found similar” with the man in the reference photographs, which featured Chauhan.
“Body structure and walking style of the person appears to be similar as that of the body structure and walking style of the person in the files,” the officer said.
She also, however, added that certain comparisons could not be done. “The comparative features of the man found in the video file could not be extracted due to night vision, distance and height of the camera. However, the outline of head and shoulder were found similar to the person marked in the other video files,” she had told the court.
While the incident occurred on the intervening night of September 9 and 10, last year, and the victim was found injured, Chauhan was arrested subsequently based on CCTV footage and eyewitness statements.
In its detailed order, the court has relied on the gait test, stating that the accused’s identification from CCTV footage is corroborated by the deposition of the expert who conducted the analysis.
“PW 31, an expert in her evidence, elaborately explained what is meant by gait test, how they compare the movement of the suspect and the sample video. In her evidence, she made it clear that they can compare the photographs and the clothes also with the help of images in the CCTV. They compared the clothes on the basis of its colour, pattern, size,” special judge H C Shende said.
The court added that nothing was elicited from the cross-examination of witnesses related to the gait analysis by the defence lawyer and that their deposition cannot be discarded.
Gait analysis, still at its initial stage, has opinions divided on its accuracy and reliability.
Last year, dismissed Mumbai Police officer Sachin Waze was made to undergo a gait test after a man was seen in a loose and large white kurta – initially thought of as a PPE kit – at the spot where a vehicle was parked near the residence of industrialist Mukesh Ambani in Mumbai with gelatin sticks.
The NIA said that a gait test was done to confirm that the person in the CCTV camera footage was Waze, though his face could not be seen, as the person in the footage had covered his head.
The gait test was also used in a murder case in Tamil Nadu, last year, and for identification of the assailant of journalist Gauri Lankesh in Karnataka in 2017. Further, it was used in Surat in a rape case, where the investigators said that the analysis enabled them to compare the walking style and body movements of the accused as well as other factors.
In the Saki Naka case, the prosecution, while submitting final arguments, said that there has been no precedent in Maharashtra on the use of the “gait test” but that cannot be a ground to discard the evidence.
Gait analysis was initially used as an evaluation method for diagnosis of causes of injuries, posture-related problems, conditions affecting walking or even for athletes to run more efficiently before it also become a forensic tool for identification.
The first known incident where gait analysis was admitted as evidence was in a criminal trial in London in 2000 against a man booked for a series of robberies. The forensic expert, a consultant podiatrist, Haydn Kelly, had said that less than five per cent of the British population’s “walking mechanics” was similar to the suspected thief’s. In other countries, including China and Japan, an artificial intelligence driven identification system helps authorities identify persons from their manner of walking.
The tool, which is still at its initial stage, has its many limitations, including the patterns of analysis that are still developing. Investigators said that it may not be as accurate as a DNA test but there are various factors used to determine the comparison, including the length of the stride of the person, height and swinging of hands to reduce errors.
Earlier, while there was reliance on eyewitnesses, CCTV footage coverage in most cities has brought a new tool in evidence.
Mumbai Police, for instance, had announced last year that 3 lakh CCTV cameras will be installed across public places. During crime detection, CCTV cameras installed by housing societies, shops and establishments are also accessed by the police to zero in on suspects and clues, pushing investigators towards tools like gait analysis.
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