While one of the three lawyers has been identified as Vikram Singh Chauhan, names of the other two have not been disclosed by the police.
All three of them were sent summons on Wednesday and asked to appear before the police at 3 pm.
Delhi Police Commissioner B S Bassi said the police will move court and obtain warrants if the three lawyers failed to do so.
Bharatiya Janata Party MLA O P Sharma, who was caught on camera beating a Communist Party of India activist at Patiala House court on Monday, joined the probe on Thursday, a day after he was served a similar summon.
The Delhi Police has been under attack for not taking action against those involved in the assault at the court complex on Monday and on Wednesday.
Chauhan, who was caught on camera assaulting journalists, students and teachers of JNU at Patiala House court complex on Monday, once again led a brazen attack on journalists and JNUSU president Kanhaiya Kumar at the court premises on Wednesday.
Later, a person who identified himself as one Surendra Tyagi came outside the court on Wednesday and claimed that he was among the attackers too. Boasting about his action, he confronted the media saying, "We have done our job for today."
However, the police have so far found no video clip in which Tyagi can be seen assaulting anyone and said that his claims are to be verified.
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