The Central Bureau of Investigation (CBI) filed a charge sheet against four accused in a local court in Hathras on December 18. 

In its charge sheet, which has been viewed by IANS, the CBI said that during the course of investigation, it collected soil, dried vegetative material, including inflorescence of bajra, from the crime of scene, where the incident allegedly took place on September 14, and the samples were analysed by experts at the Central Forensic Science Laboratory (CFSL) in the national capital. 

It also said that it also got the forensic psychological assessment and layered voice analysis test of the four accused and others by CFSL experts. 

The CBI, just eight days before filing the charge sheet, also got the brain electrical oscillation signature (BEOS) and polygraph test of the four accused at the Directorate of Forensic Science in Gujarat's Gandhinagar on December 10. 

The CBI said that it has submitted the reports of the CFSL with the court. 

It is not clear what the results are but they may hold significance for the probe, an agency official said. 

The Dalit woman was allegedly gang raped by four upper-caste men in Hathras on September 14 this year. She died on September 29 at Delhi's Safdarjung Hospital during treatment. 

The police's handling of the case -- particularly the late-night cremation of the victim allegedly without the family's approval -- led to angry protests across the country. The officials, however, maintained that the cremation was done "as per the wishes of the family". 

The Yogi Adityanath government faced a lot of flak on the handling of the case which was later transferred to the CBI. 

The CBI, which has named Sandeep Sisodiya, Luvkush, Ravi and Ramu -- all in judicial custody -- as the accused, had set up a special team to probe the case. The team has recorded the statements of the victim's family. 

It also also said that the friends of Sandeep, namely Ramu, Ravi and Lavkush, were also questioned about their whereabouts during the time of incident. 

"Ravi claimed that he went to deposit milk at a milk collection centre. However, it was established in the investigation that the milk was deposited at 7.34 a.m. and thereafter he was not able to explain his whereabouts," the CBI said. 

Similarly, Ramu claimed that he was working in Madhusoodhan Dairy at that time. "However, while examining the staff of the dairy it was revealed that the attendance of the employees were maintained manually and there was no rigid restriction on the movement of the workers, and no fixed time," it said. 

Lavkush could not also explain his whereabouts satisfactorily, the CBI said. 

"However, immediately after the incident, he was available near the scene of crime," the CBI contended.