OTTAWA - The head of the RCMP says mandatory disclosure of detailed police files to defence lawyers can cause problems in terrorism and other criminal prosecutions.

Commissioner William Elliott told the Air India inquiry it's a "significant burden" for police to meet requirements to disclose background material before a trial begins.

He acknowledged, however, that he doesn't know quite how to fix the problem.

The head of the inquiry, former Supreme Court judge John Major, suggested it might be possible to carve out an exception to disclosure in anti-terrorist cases to keep sensitive national security information secret.

But Elliott said that may be difficult to do in practice without infringing on defendants' constitutional guarantees under the Charter of Rights.

The issue of court disclosure of sensitive material has been a key issue for the inquiry, which is examining the aftermath of the 1985 Air India bombing that took 329 lives.