Natalie Belmonte Murder: Fla. man raped adoptive mother before killing her in 2011, prosecutors say

(CBS) FT. LAUDERDALE - Gerard Lopes Belmonte, a Florida man charged in the 2011 murder of his adoptive mother, is headed to trial Monday and for the first time prosecutors are offering a motive in the case: they say he raped her.

Prosecutors said during a court hearing Wednesday that Gerard Belmonte killed his 43-year-old adoptive mother, who was also his first-cousin, to cover up having raped her, the Broward Palm Beach New Times reports. They say DNA tests show Gerard Belmonte's semen was found in the body of Natalie Belmonte. Gerard Belmonte was 22 at the time of the alleged crime.

Natalie Belmonte vanished July 17, 2011 after having attended a party with her son. Gerard Belmonte reported his mother missing the next morning, saying he woke up in their Pembroke Pines home and she was no where to be found. Her body was discovered in a wooded area three days later.

Police arrested Gerard Belmonte the same day and charged him with murder after obtaining surveillance footage that reportedly showed him putting his mother's body in the trunk of her Lexus. He has pleaded not guilty.

According to the paper, Gerard Belmonte has a history of mental health issues and has previously served time behind bars.

During the court hearing Wednesday, Gerard Belmonte's defense team reportedly argued that he and his adoptive mother had a consensual sexual relationship, the paper reports.

Natalie Belmonte's sister, Michaela Teixeira, refuted the defense's claim during the hearing Wednesday, insisting there was "absolutely no way" her sister had a consensual sexual relationship with her adopted son, the paper reports.

The judge ruled that the DNA evidence found by investigators would be admissible in the trial, according to the paper.