Privileged communication between client and legal adviser:

Police custody can be granted only during first 15 days of the custody after arrest. Therefore, if an accused has already spent more than 15 days in judicial custody, he cannot be remanded to police custody.

Professional communications with a lawyer is a privileged communication under Section 126 of the Indian Evidence Act. No lawyer is permitted to reveal the same without his client's consent. However, there are certain exceptions mentioned in that section. Moreover, it appears that this section does not apply if the client wants to disclose what advice he received from his lawyer.

It goes without saying that third degree is NOT permitted under law. The police officer can be prosecuted for such custodial violence. But, it is also a fact of life that such third degree treatment does take place in police custody even though it is not permitted under law.

Now, the question is whether the lawyer has given any illegal advice to the client? Or, whether any offence is committed by the lawyer? You have not disclosed these details in your question. The answer depends on these details. In the absence of these full details in your question, I can only say in general that if the lawyer has committed any offence while dealing with his client, and if the client discloses that information to the police (either due to third degree or otherwise), there is of course the possiblity of the police taking action against the lawyer.