A West Michigan man already serving time in prison on drug charges was sentenced to spend the rest of his life behind bars for murdering an Ypsilanti Township man.

Mark Porter, 35, received the mandatory life sentence last week for gunning down 41-year-old David Gibson outside his residence in the Swan Creek manufactured home community in October 2006.

Mark Porter

Jurors convicted him of first-degree murder, felony murder and conspiracy after deliberating for about three hours earlier this month, Washtenaw County court records show.

Investigators suspected Porter, of Battle Creek, in the drug-related crime but lacked evidence to bring charges. His girlfriend, Jo Ann Caldwell, was convicted of first-degree murder in Gibson’s death in 2007 and received two life sentences. Her appeal was denied last year.

Washtenaw County sheriff’s detectives re-interviewed Caldwell, and she testified at Porter’s trial.

Art Aisner is a freelance writer for AnnArbor.com. Reach the news desk at news@annarbor.com or 734-623-2530.