A public inquiry into the 1985 Kanishka bombing will scrutinise the Canadian security agency's decision to erase wiretap recordings of the prime suspect, a step the victims' families claim jeopardised the prosecution's case, as it resumes hearing after a three-month break.

The hearing in Ottawa that will begin on Monday will also delve into the rocky relations between the Royal Canadian Mounted police and the Canadian Security Intelligence Service that have been blamed for the failure to prevent the
worst terrorist act in Canadian history that killed 329 people mostly of Indian origin and apparently affected the probe.

The inquiry headed by Justice John Major that began in June 2006 will now turn its attention to the investigation that took place after the bomb destroyed the Air India Flight 182 near Ireland as it was en route from Canada [Images] to India.

It has already heard what intelligence officials may have known about a conspiracy to bomb the flight.

The decision by CSIS to erase audiotapes of phone conversations involving the alleged mastermind Talwinder Singh Parmar has often been questioned by the victims' families.

The erasure policy has been explained previously as a simple issue of not having enough space to store reels and reels of tape.

The policy at the time was to erase tapes once they had been translated, but the transcripts in this case have been questioned because the conversations were not transcribed verbatim.

Tape erasures by CSIS were a significant issue in the trial of Inderjit Singh Reyat, the only person convicted in relation to the bombing.

A Parmar associate, he was found guilty on a reduced charge of manslaughter.

The issue also surfaced in the separate case of Ripudaman Singh Malik and Ajaib Singh Bagri, who were accused of playing senior roles in the bombing.

They were acquitted following a $130-million trial in Vancouver two years ago, in a verdict that outraged the victims' families.

The commission will also explore new evidence from India, the current debate surrounding terrorist trials and the witness protection programme.

The Security Intelligence Review Committee, the civilian watchdog for CSIS, reported in 1992 that nothing of value was lost by erasing the wiretaps. But some have criticised that finding for lacking proper analysis.

There has yet to be a clear answer as to why the Justice Department waited eight months after the bombing before instructing the spy agency not to destroy wiretaps of the prime suspect.

Also, questions surround CSIS's decision to erase bombing-related interviews in 1987, two years after the terrorist incident.

The various players have long offered conflicting versions of what happened and who was to blame for the erasures, and sources say dramatic differences will likely be evident again when they appear before Major, media reports said in Toronto.

Mark Freiman, the chief counsel for the inquiry, wouldn't speculate on that possibility, but he did acknowledge that a key theme will be the "complex issue" of how to transform raw intelligence into evidence that can prove a case beyond a reasonable doubt.