A former member of the Aum Shinrikyo cult pleaded not guilty Monday in his trial appealing the life sentence he received for his role in the group's 1995 sarin nerve gas attack on the Tokyo subway system.

Katsuya Takahashi, 58, was sentenced to life in prison by the Tokyo District Court in April 2015 after being convicted of murder and other charges over his role as a driver for one of the cult members who released the deadly poison in subway cars on March 20, 1995.

The appeal trial kicked off Monday afternoon at the Tokyo High Court.