WARSAW, Poland (AP) — An aide to Poland's former prime minister went on trial with four others Thursday on charges connected to the 2010 plane crash that killed President Lech Kaczynski and 95 others.

The Polish government is now ruled by the conservative Law and Justice party led by Kaczynski's twin, Jaroslaw Kaczynski, who has accused former Prime Minister Donald Tusk, a liberal, and his government of contributing to the death of a president with whom they did not get along.

Tusk is now the European Union president.

The charges were brought before a Warsaw court by families of some of the victims, who say 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. Polish and Russian investigations have concluded the crash was the result of crew errors coupled with adverse conditions.

Among the defendants is the head of Tusk's office in 2010 and the former Polish ambassador to Spain, Tomasz Arabski. He was absent from court on Thursday. In December, the current government cut short his term as ambassador.

In a recent interview for the Dziennik Gazeta Prawna newspaper, Arabski said he has a "clear conscience" and that he believes the pilots were under pressure from the passengers to land despite the poor visibility.

Four other defendants argued Thursday that Lech Kaczynski's office was chiefly responsible for the flight that was taking the president and other top officials to ceremonies honoring the thousands of Polish prisoners of war killed in 1940 by the Soviet secret security.

If convicted, the defendants could face up to three years in prison.