"There is some foulplay. He cannot commit suicide. He is not such a person that he can commit suicide. He was very happy with the way the trial was going on," lawyer V K Anand, who represents Singh and his brother Mukesh, alleged.
Anand also said he would move the Supreme Court for shifting the trial from Delhi as he feels that the accused are not safe here.
Singh, 33, allegedly hanged himself with the help of his clothes from the grills of his cell in Jail No 3 around 5 am, jail officials said.
Lawyer A P Singh, appearing for Vinay Sharma and Akshay Singh, said that Ram Singh was "killed by jail authorities" and that Tihar is no longer safe for undertrials to be lodged in.
"Now I want that my clients should be released on bail as Tihar is no more safe place for them also. They will also be killed," he further said.
The sixth accused in the case is a minor who is facing proceedings before the Juvenile Justice Board and he has also been charged with rape and murder of the girl.
A P Singh said, "If Ram Singh was in depression, he would have committed suicide, three months back when he was arrested. He and our client were very much positive. I want CBI inquiry into the matter and against the officials who were on duty."
M L Sharma, who appeared for Singh initially, also alleged that Singh was killed by police.
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