An Auckland man has admitted manslaughter and driving-related charges after a triple fatal in Hamilton nearly three years ago.

Reuben William Maharaj, of Glenfield, was due to stand trial in the High Court at Hamilton next week on three charges of three charges of manslaughter of Jeremy and Tania Kay and Grace Hill and one charge of dangerous driving causing injury to Mitchell Kay.

However, in a brief appearance via audio visual link before Justice Graham Lang today, Maharaj entered guilty pleas, bringing to an end a long fight for justice by the Kay and Hill families.

Mitchell Kay had just gone to pick up his parents and girlfriend, Hill, from a 21st birthday on just after midnight on November 11.

At the same time, Maharaj, who had been diagnosed with schizophrenia but was unmedicated at the time, had earlier fled his parents in one of their vehicles from their North Shore home after an argument.

Other motorists had noticed Maharaj's "aggressive" driving on the journey south before he entered Avalon Dr.

About 800m south of the roundabout, Maharaj accelerated and drove with a sudden or sharp swerve, crossing the centre line into the oncoming northbound traffic and collided with the Holden Trax being driven by Kay.

The Holden Trax, driven by Mitchell Kay, was left destroyed after the head-on crash on Avalon Dr. (Photo / Police)

Witnesses described seeing a "big puffy [sic] of black smoke" coming out of Maharaj's exhaust, and appeared to be speeding up, before he was seen driving on the wrong side of the wrong.

Kay was in his correct lane, driving about 78km/h, and tried to take evasive action, by braking and swerving. The vehicles ultimately collided, killing his parents and girlfriend.

Outside court this morning, Kay's grandmother and Jeremy Kay's mother, Robbie Kay, together with Linda Kay's mother, Linda Rowe, said they were pleased by the guilty pleas and said it was a relief.

"We're just relieved that it's over and he's pleaded guilty after nearly three years."

The remains of the vehicle Reuben Maharaj was driving on the night of November 11, 2018. (Photo / Police)