The DNA of Idelfonso Velez was discovered on the kitchen knife authorities say was used to stab Trisha Bennett and Angel Ortiz to death in 2010.

Velez, 29, of Framingham, is on trial in Middlesex Superior Court on two counts of first-degree murder in the deaths of Bennett and Ortiz, who were found stabbed to death inside their Hudson apartment in May 2010.

Andrea Borchardt-Gardner, a senior DNA analyst with Bode Technology in Virginia, told jurors Thursday she tested several DNA samples from the handle, tip and the recasso, the portion of the knife where the handle meets the blade. She found the samples matched Velezs DNA.

The probability of a randomly selected, unrelated person matching the DNA from the profile on the handle, tip and recasso is 1 in 2.8 quintillion, said Borchardt-Gardner.

The current world population is estimated to be about 7 billion, said Borchardt-Gardner.

"I can say to a reasonable degree of scientific certainty that Mr. Velez is the source of that DNA profile," said Borchardt-Gardner.

Borchardt-Gardner also testified Thursday that Bennetts DNA was found on the recasso portion of the knife. The probability of a randomly selected, unrelated person matching Bennetts DNA from the recasso section of the knife is 1 in 3.1 trillion.

Earlier this week, Massachusetts State Police Trooper Kevin Murphy said Velez told him that he entered Ortiz and Bennetts bedroom the night of the murders after hearing Bennett scream "baby, baby, baby."

Velez told Murphy that a man with a knife was standing over Ortiz and then attacked him before dropping the knife as he was running from the apartment. Velez then picked up the knife for his safety and placed it in the kitchen sink, said Murphy.

Alanna Frederick, a chemist with the Massachusetts State Police, also told jurors that DNA tested from a swab of blood spatter on the left thigh of the jeans Velez wore the night of the murders matched the DNA of both Velez and Bennett.

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Prosecution: Velez' DNA found on knife used in Hudson murders