Another troubled episode in the life of Adam Kearns - son of the Black Widow murderer Helen Milner - has come to a head in court today. 

The 26-year-old had methamphetamine and alcohol in his system when he sped at 111km/h in a 50km/h zone in December 2015.

Kearns hit a parked car, his female passenger was critically injured and his other passenger Nicholas Morrison died at the scene.

He was sentenced to four and a half years in jail in the Christchurch District Court this morning.

Kearns helped convict his mother of fatally poisoning her second husband in 2009.

He was then found guilty of punching and stomping former All Black Justin Marshall in Queenstown in 2014.