The Leipzig state court in Saxony, eastern Germany, sentenced Uwe J. to robbery with fatal consequences, the Bild newspaper reported.
The 47-year-old confessed the crime and can apply for parole after 15 years. But possible early release for good behaviour has been ruled out.
Uwe J. attacked both former in-laws, Erhard and Marlies G., with a hammer in their home in Pegau, Saxony, on 25th March this year.
He reportedly went over to demand money as he had spiralling debts and had just lost his house and had a failed drywalling company, Bild reported. But the couple refused.
It was then that he used the hammer he had brought with him to first strike his former mother-in-law, 68, on the skull. He then hit Erhard G., 72, who was trying to protect his wife. He dealt them 12 blows in total.
A police woman told the court that the scene resembled a "horror film".
“The floor was bloodstained, the kitchen was bloodstained. You could see how the man had tried to get out of the kitchenette to get help,” she said.
Uwe J. left the scene with €150 in cash and his victim's bank cards. Three days later, one of the couple’s grandchildren found them still lying on the kitchen floor, covered in blood.
It was 11 days after the discovery that the police special forces stormed Uwe J.'s house in Groitzsch. He had already fled, and officers eventually caught up with him near the town of Altenburg also in Saxony.