Garrison, who played David "Tweener" Apolskis on the hit US show, pleaded guilty to vehicular manslaughter and drunken driving in May this year. He caused a crash which killed a 17-year-old high school student in December 2006.
Dominic, better known as Lincoln Burrows on the programme, has admitted that he has his own alcohol problems, and has taken Garrison to a number of Alcoholics Anonymous meetings with him.
Purcell has promised that he will continue to be there for Lane "110 percent". He explained: "The admirable thing about Lane is that he's accepted full responsibility for his actions."