the killing took place in the city of Heilbronn
The 27-year-old defendant, named as Abubaker C, is accused of strangling the 70-year-old woman to death after breaking into her home on May 19 last year and leaving a series of Arabic and religious messages around the house.
The victim's 74-year-old husband told the court in Heilbronn, Germany, he found her body with her hands tied and holding a cross.
He said that his family were committed Catholics.
A phone and an undisclosed sum of money had also been taken.
Prosecutors allege Abubaker killed the woman because she was "a disbeliever from his point of view".
But the accused claimed he is the victim of a religious conspiracy during the trial.
DNA taken from the crime scene matched the defendant's, while cotton fibres from a jacket and shoe prints also linked him to the murder, the judge said.
Several witnesses also identified him as the attacker.
The defendant, speaking in Punjabi through a translator, dismissed all allegations as "lies".
He said he found a bag full of money and valuables at a train station on Heilbronn the morning after the murder.
He claimed he had been out on the night of the killing but not in the Bad Friedrichshall district, where the murder took place.
He said he was a victim of a religious conspiracy and had nothing against Christians, bizarrely adding "deadly violence" could be used against them in self-defence.
The defendant refused to give a precise date of birth, and changed his country of origin from Pakistan to Saudi Arabia.
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The court also heard he moved to Germany in 2013 and came from a family so rich his previous job involved him counting his parents' money.
The trial continues.