FT. LAUDERDALE (CBSMiami) – After a week of testimony, the murder trial of a Pembroke Pines man who is accused of killing his adoptive mother is coming to a close.

Lopes is accused of killing the woman who adopted him, Natalie Belmonte, in 2011. Family members say Belmonte adopted Lopes, 23, who is also her cousin, 15 years ago after his father died.

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On Thursday the jury in the case against Gerard Lopes listened to gripping testimony from the sister of the victim, 43-year-old Natalie Belmonte.

Belmonte was beaten and strangled and her body dumped in a wooded area not far from home in July 2011.

(Photo Credit: Pembroke Pines PD) Natalie Belmonte

(Photo Credit: Pembroke Pines PD) Natalie Belmonte

Lopes, 21-years-old at the time of the murder, had been with his mother at a graduation party and prosecutors say when they returned home, he had a confrontation in her bedroom and proceeded to rape and kill Belmonte.

“She was a good mother. She treated him like her other children and wanted the best for him, like any mother would want,” said Michaela Teixeira, Belmonte’s sister.

Teixeria said Belmonte was her best friend and someone she spoke with every day. She became frantic when her sister disappeared. But she said Lopes was surprisingly calm.

After police named Lopes as a suspect, she said that she spoke to her nephew.

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“I asked him if my sister was calling for me. What happened to her, and from the beginning he said I don’t remember but this time he said I remember but I can’t tell you. I have to think of my trial,” recounted Teixeria.

Prosecutors also had a DNA expert testify that semen that was found inside Belmonte during an autopsy. Christopher Comar testified, “the odds of finding someone else within the population other than Lopes is rarer than 1-in-30 billion.”

Still Lopes has said that the sex was ‘consensual’ and his defense attorney tried to press Belmonte’s sister on whether she knew ‘everything’ her sister did.

“What relevance is that,” Teixeira snapped at one point.

Prosecutors maintain Belmonte was ‘only’ a mother to Lopes and showed the jury cards he had written to her including a birthday card which read, “You are the best mother a son can have.”

Closing arguments are scheduled for Monday. Then the jury will decide whether Lopes is guilty of murder.

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Lopes has pleaded not guilty. If convicted, Lopes is looking at life in prison.