(Reuters) - An Indonesian court on Tuesday sentenced a U.S. man to 18 years in prison for the murder of his girlfriend's mother, whose body was found stuffed into a suitcase on the resort island of Bali.

Tommy Schaefer, from the Chicago area, was arrested with his girlfriend, Heather Mack, last August after staff at a luxury hotel discovered the body of Mack's mother, Sheila von Wiese-Mack, in an abandoned suitcase in a taxi.

Schaefer was charged with premeditated murder after he said in court he had killed Wiese-Mack in self-defense.

Mack was charged with being an accessory to murder and a verdict on her case also expected later on Tuesday.

Schaefer was seen crying in court after presiding Judge Made Suweda announced the murder verdict and sentence in Denpasar District Court.

"Although I do take full responsibility for my actions, I am not a murderer," Schaefer told Reuters after hearing the verdict.

It was not immediately clear if the defense planned to appeal.

Bali police, assisted by the U.S. Federal Bureau of Investigation, conducted a four-month investigation into the killing, including a re-enactment with the defendants at the luxury hotel where the victim's body was found with bruises on her arms and broken fingers.

Other evidence submitted to prosecutors included CCTVhttp://images.intellitxt.com/ast/adTypes/icon1.png footage showing the couple speaking to a taxi driver after dropping the bloodied suitcase along with other luggage outside the hotel.