A west Michigan man was found guilty of a murder committed in 2006 in Ypsilanti Township and faces mandatory life imprisonment at sentencing next month.

Jurors found Mark Porter, 35, guilty of first-degree murder, felony murder and conspiracy in the shooting death of David Gibson following a three-day trial in Washtenaw County Circuit Court.

Porter is already serving a 20-year prison sentence on drug charges.

Neighbors found Gibson’s body outside his residence in the Swan Creek manufactured home community on Oct. 28, 2006. The 41-year-old was shot multiple times.

Washtenaw County Sheriff’s detectives arrested Jo Ann Caldwell, Porter’s girlfriend, about a week later, and she was convicted of first-degree murder in 2007. She was sentenced to two life terms in prison and lost her appeal last summer, records show.

Authorities suspected Porter, of Battle Creek, was involved but couldn’t prove it. Court officials said Detective Mark Neumann testified he visited Caldwell in prison on multiple occasions and talked about her importance in the case.

She testified for the prosecution at Porter’s trial and gave detailed accounts of the drug-related crime. Porter denied killing Gibson when he testified, officials said.

Jurors deliberated for roughly three hours.

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