Answer on @Quora by Malwinder Jit Singh Waraich to What happened to people who identified Bhagat Singh in court?
Answer by Malwinder Jit Singh Waraich:
We have to make a distinction b/w the witnesses who appeared or identified the revolutoinaries during their trials.
Among them were quite a number who are technically called, formal witnesses. The librarian of Dwarka Das Library, Raja Ram Shastri a lifelong admiror of Bhagat Singh also appeared as a prosecution witness (PW: 427) Reference * to verify a book issued to Sukhdev.
Similarly there were number of witnesses of recovery which included the family members of the revolutionaries.
Those witnesses who had been comrades of the revolutionaries and turned approvers played a key part in their prosecution because a number of secrets were revealed only by them, in the court. However, among them also there were those like Hans Raj Vohra who confined themselves mostly to the facts already known to the police.
The worst were insiders like Jai Gopal and Phaninder Ghosh who invented false stories at the behest of the police. It was only these two who were targeted by the revolutionaries. Jai Gopal escaped the assault on him in a court in Jalgaon, and Phaninder Ghosh was put to death by Baikunth Shukla. Reference *
As far Sobha Singh, he's a class by himself because he was the only witness in the Delhi Assembly Bomb Case, who claimed that he had actually seen Bhagat Singh and BK Dutt hurling the bomb. Significantly during his cross examination his version was found to be doubtful and the session judge in his judgement has hinted to that affect. Refrence *
 The Hanging of Bhagat Singh Vol 2A: Select Tribunal Proceedings with Sukhdev's Remarks. Publication: Unistar Books, 2010
 The Hanging of Bhagat Singh Vol 1: Complete Judgements and Other Documents. Publication: Unistar Books 2005