An investigator at the fire-damaged multimillion-dollar home in Northwest Washington where four people were slain. The victims are 46-year-old Savvas Savopoulos, his 47-year-old wife, Amy Savopoulos, the couple’s 10-year-old son and the family’s housekeeper, Veralicia Figueroa. (AP; Tony Powell/Washington Life Magazine; Veralicia Figueroa's family)

The tragedy in May 2015 permeated the nation’s capital. The bodies of a father, a mother, their 10-year-old son and the family’s housekeeper were found in a burning multimillion-dollar home in a quiet upper Northwest neighborhood, less than a mile from the vice president’s official mansion.

The victims, investigators would soon determine, had been suffocated, beaten, stabbed and set on fire.

As shocked residents speculated about who could have committed the crimes — and why — police said they believed it probably would have taken more than one person to carry out the killings of Savvas Savopoulos, 46; his wife, Amy Savopoulos, 47; their son, Philip, 10; and their housekeeper, Veralicia Figueroa, 57.

The break in the case came with an unlikely piece of evidence: a piece of crust from pizza delivered to the home when police say they believe the killer was inside. On it, police said, they found the DNA of a Lanham, Md., man who was a former employee at a Savopoulos family business.

On Tuesday, the trial is set to begin in D.C. Superior Court for that man, the only suspect arrested in the slayings. Daron Wint, 36, is charged with 20 counts, including first-degree murder, kidnapping and other crimes. He has pleaded not guilty.

Federal prosecutors allege that Wint held the victims hostage as he ordered Savvas Savopoulos to have $40,000 delivered to the house as ransom. Wint then killed the victims, prosecutors allege, and made off with the cash, fleeing in the family’s blue Porsche.

Daron Dylon Wint (Oswego County Sheriff’s Department/Reuters)

But Wint’s attorneys have suggested a stunning defense — pointing the finger at another person. In pretrial hearings and motions, his lawyers with the District’s Public Defender Service said they uncovered evidence implicating someone else as the killer. Over the objections of prosecutors, Judge Juliet McKenna allowed the defense to wait until trial to publicly disclose their alternate suspect’s name.

Over the course of a trial expected to last about eight weeks, jurors will decide which version to believe. A panel of nine men and seven women, including four alternate jurors, was selected last week.

Late Friday, defense attorneys filed a motion contending they had learned that D.C. police and the Department of Forensic Sciences may have improperly handled some evidence, including a knife found in the home’s basement. The defense attorneys asked for additional details on how the evidence was handled. As of Monday evening, prosecutors had not yet responded.

Savvas Savopoulos was president and chief executive of American Iron Works, a leading custom steel and iron manufacturing company that helped build Capital One Arena, formerly known as Verizon Center, and CityCenterDC. His wife was a devoted mother who cared for their three children and had an interest in the prevention and treatment of childhood concussions, her friends said.

The home where three members of the Savopoulos family were held and killed along with their housekeeper in 2015. (Jonathan Newton/The Washington Post)

Philip was a student at St. Albans School in the District. The couple’s teenage daughters, Abigail and Katerina, were away at boarding schools during the attack.

Figueroa, a wife and mother, had moved to the Washington area from El Salvador and hoped to return to her native country, according to her family.

In the months leading up to the trial, prosecutors and defense attorneys filed hundreds of pages of court documents that offer a glimpse of the road map each side plans to follow as they present their cases over the next two months.

Prosecutors said they may call as a witness a D.C. jail inmate who said Wint admitted to him that he participated in the killings with “another individual from Guyana.” Wint was born in the South American country and moved to the United States in 2000 and became a permanent resident after obtaining his green card.

Wint is a onetime employee of Savopoulos’s iron supply company and has a long history of alleged assaults and threatening behavior, according to law enforcement and court records. In the mid-2000s, four people — including his father and a housemate — petitioned for restraining orders against him, the records show.

In court filings, prosecutors gave brief summaries of autopsy reports that describe the brutality of the attacks in the Savopoulos home.

There was evidence all three adults had been restrained, according to court papers. Adhesive tape residue was found on Amy Savopoulos’s wrists and ankles and on Figueroa’s wrist. Authorities say they think Savvas Savopoulos’s wrists and ankles were bound with a necktie or zip tie.

Authorities allege Wint held his victims hostage overnight on May 13, 2015. That evening, they say, he forced one of the victims to order a pizza that was delivered to the house by Domino’s. The pizza boxes were later found in a bedroom, according to court papers.

Police said they think the Savopoulos family members and Figueroa were killed on May 14, after the ransom money was delivered by Savvas Savopoulos’s assistant, Jordan Wallace.

Savvas and Amy Savopoulos were both beaten with a baseball bat and stabbed, according to the court papers. Her right middle finger was bruised, injuries consistent with her attacker trying to pull a ring off, prosecutors wrote in court papers.

Authorities think Philip Savopoulos was stabbed with a sword, probably the one his father kept as part of his martial arts collection.

Figueroa had been stabbed in the neck but had the fewest injuries. Medical examiners concluded she had a history of heart disease and probably suffered a heart attack during the incident, according to court documents.

Police said in the affidavit for Wint’s arrest that the elaborate crime probably “required the presence and assistance of more than one person.” But there were no additional arrests.

Prosecutors said in court papers that, in addition to the $40,000 and the Porsche, an “unknown amount of money” was taken from Savvas Savopoulos’s wallet. Portions of the home’s electronic security system and two iPhones were also taken.

Authorities say Wint, driving the Porsche, sped down New York Avenue in Northeast Washington into Prince George’s County and then set the car on fire. His DNA was later found on a piece of clothing discovered inside the vehicle, prosecutors said. Prosecutors said he later fled to New York.

When police arrested Wint about a week after the killings, they found at least $10,000 in cash and dozens of lottery tickets in a box truck linked to the group with whom he was traveling. He was with four people, including two family members.

Wint’s attorneys plan to argue that detectives failed to thoroughly investigate the case after Wint’s arrest, missing evidence that they say would have directed them to another suspect.

In their filings leading up to the trial, the defense attorneys also asked for additional information regarding their alternative suspect, who they say gave “false” information to detectives about his whereabouts on the evening of May 13 into the morning of May 14.

Prosecutors have said in the filings that they are seeking life without parole should Wint be convicted.

Family members of the victims declined to speak publicly about the case as it neared trial. Amy Savopoulos’s father, James Martin, has attended the majority of hearings leading up to the trial, including jury selection. Several of Figueroa’s family members have also been in attendance.

The Savopoulos house was restored after the fire and put up for sale. But no buyer emerged. Since then, it has since been razed, leaving an abandoned lot with a couple of “For Sale” signs.

Magda Jean-Louis contributed to this report.