In 2015, an ATF investigator leaves the Northwest home where four people were found dead, including Savvas Savopoulos, Amy Savopoulos and their housekeeper, Veralicia Figueroa. (AP, Tony Powell/Washington Life Magazine, Courtesy of Veralicia Figueroa's family)

The attorneys for the man charged with the 2015 killings of three Upper Northwest Washington family members and their housekeeper say they have evidence someone else was responsible for the killings that they plan to introduce during the September trial.

In their latest filing Friday, D.C. public defenders Judith Pipe and Jeffrey Stein did not identify who the other person is and argued to D.C. Superior Court Judge Judith McKenna — over prosecutors’ objections — that they do not have to reveal the details of their defense until trial.

“The court should reject the government’s attempts to secure pretrial discovery of defense theory, the identities of any purported third-party perpetrator and the evidentiary basis supporting” such defense, Daron Wint’s attorneys wrote in their filing.

A hearing is scheduled Friday, at which point McKenna could rule on whether defense attorneys would be required to reveal their defensive strategy or allow them to wait until trial.

Wint, 36, of Lanham, Md., is charged with murder and other crimes in the killings of businessman Savvas Savopoulos, 46; his wife, Amy, 47; their son Philip, 10; and their housekeeper, Veralicia Figueroa, 57.

He has pleaded not guilty to all charges.

Daron Wint (Reuters)

Police have said the four victims were held captive the evening of May 13, 2015, and that their attacker fled with $40,000 in ransom that had been delivered to the stately home in the 3200 block of Woodland Drive NW, the neighborhood where the vice president’s official mansion is also located. The family’s burned-out home has since been demolished.

Prosecutors say Wint beat, strangled and stabbed his four victims before setting the house on fire. Police discovered the bodies after firefighters were called to the home.

Authorities initially said they thought Wint did not act alone, but Wint remains the sole defendant in the slayings.

Wint’s trial is scheduled to begin mid-September following what attorneys expect to be a lengthy jury selection process as a result of the media attention the case has drawn. The trial is expected to last about two months, attorneys have said.

Although Wint’s attorneys did not name another suspect, in an earlier court filing, they cited one person they said had provided homicide detectives with “false information” about his whereabouts on the night and early morning of the killings. The attorneys requested additional information regarding this person. The name of the person was redacted from court files.

Wint once worked for a Savopoulos family business, American Iron Works.

An arrest warrant was issued for Wint after his DNA was found on pizza crust at the scene. His DNA was later found on a neon-green construction vest that was inside a blue Porsche stolen from the home, prosecutors said. Since then, hundreds of forensic samples from the scene were collected and studied, according to recent court filings.

Longtime D.C. defense attorney Bernard Grimm said Wint’s attorneys face a difficult challenge to overcome DNA evidence with jurors and to prove their theory of an alternative suspect is more credible than the findings of the investigation conducted by D.C. homicide detectives and prosecutors.

“They could have enough evidence to say Wint was on the scene, but wasn’t the killer,” said Grimm, who is not associated with the case. “But that may be hard to prove. Jurors love DNA.”

Grimm said Wint’s attorneys may argue that their client was not the killer, but instead may have been the getaway driver or played a lesser role in the case in an effort to explain his DNA being present.

“The attorneys are going to have to prove they have a guy who has a motive, who they can put on the scene, who has opportunity and who had put the whole plan together,” Grimm said. “They’re going to have to play more of a prosecutor than defense lawyer. That’s an uphill climb.”