Canada’s long-running Air India trial entered its final stages on Tuesday, as the defense began closing arguments by accusing a key witness of lying about what she knew of history’s deadliest bombing of a civilian aircraft. Lawyers for Ripudaman Singh Malik told the court in Vancouver that prosecutors also failed to prove the wealthy businessman had the political motivation to be involved in a conspiracy by Canadian-based Sikh militants. “It is inconceivable that anybody would have participated in this crime without a political motive,” David Crossin told the court.

Malik and Ajaib Singh Bagri are charged with the mid-air destruction of Air India Flight 182 off the coast of Ireland in June 1985, killing 329 people. The plane was destroyed as it approached London for a refueling stop on its flight from Canada to India. The two are also charged with an attempt to bomb a second Air India jet over the Pacific Ocean at the same time. Investigators say that the bomb exploded prematurely, killing two airport workers in Tokyo.