An aide to Poland's former prime minister, Donald Tusk, has gone on trial with four others on charges connected to the 2010 plane crash that killed President Lech Kaczynski and 95 others.

The trial opens while political power is held by the conservative Law and Justice party led by Kaczynski's twin, Jaroslaw Kaczynski, who has accused Tusk and his officials of contributing to the death of a president with whom they did not get along.

The charges were brought before a Warsaw court by families of some victims, who say that Tusk's aides neglected their duty to safely prepare Kaczynski's flight. The plane crashed in dense fog on approach to the airport in Smolensk, Russia.

The defendants argued Thursday that Lech Kaczynski's office was chiefly responsible for the flight.