After 18 months of testimony, the Air India trial enters its final phase Tuesday in British Columbia Supreme Court as the Crown and defence present their closing arguments.

Two men, Ripudaman Singh Malik and Ajaib Singh Bagri, are charged with killing 331 people in two separate bombings on the same day in June, 1985. One bomb killed 329 people on board Air India flight 182, most of them Canadians. It was the worst mass murder in Canadian history.

The second bomb killed two baggage handlers at Tokyo's Narita Airport.

Malik and Bagri

Since the trial began in April 2003, it has heard from more than 100 witnesses, most of them for the Crown.

The witnesses have included a former employee of Malik who testified that on two occasions he discussed the alleged conspiracy with her.

Another witness told the court Malik asked him to deliver an attache case containing a bomb.

And a New York resident testified that co-accused Ajaib Singh Bagri admitted his involvement in the alleged plot.

It's expected that Malik's defence lawyers will begin presenting their arguments first. Next week it will be the turn of Bagri's defence team. The Crown prosecutors will make their submissions last.

Prosecutors claim the accused were Sikh terrorists acting out of revenge against the Indian government for its 1984 attack on the sacred Golden Temple in Punjab.

The case is being heard by a judge alone.

The Air India trial, including the nearly 20 year investigation leading up to it, is believed to be the most expensive case in Canadian legal history. Some estimates say it has cost nearly $100 million.