As Cosmo DiNardo carried out the killings of three young men in Bucks County, was his cousin Sean Kratz in on the plan, committing one of the murders and acting as lookout during the other two? Or was he being held captive by a psychopath, and too afraid for his own life to try to stop the carnage?

Those are the competing scenarios that lawyers presented to a jury on Wednesday in dramatic opening statements as Kratz’s triple homicide trial began in the July 2017 killings.

DiNardo, who pleaded guilty to killing the three men plus a fourth in the same week, will testify at the trial, Kratz’s attorney said in his opening statement. Kratz also is set to take the stand.

Prosecutors say Kratz, 22, killed Dean Finocchiaro, 19, of Middletown Township; helped while DiNardo killed Thomas Meo, 21, of Plumstead Township, and Mark Sturgis, 22, of Pennsburg; and then joined him in cleaning and covering up the evidence. DiNardo alone killed Jimi Patrick, 19, of Newtown.

“This defendant and his cousin were on a mission to kill, rob, burn, and bury bodies. That was his summer day on July 7, 2017,” Assistant District Attorney Kate Kohler told the jury. “It was just something fun to do that day, because they could.”

Kratz’s attorney, A. Charles Peruto Jr., said DiNardo told Kratz he would kill him and his family if Kratz did not kill Finocchiaro and later keep quiet about the deaths.

“The evidence will show that all four would be dead with or without Sean Kratz,” Peruto said. “He’s not the lunatic. Cosmo DiNardo is. This was somebody preyed upon by a psychopath.”

Kratz, of Philadelphia, is charged with three counts of homicide plus conspiracy, robbery, abuse of corpse, and possession of a weapon.

The gruesome homicides led investigators on an agonizing weeklong hunt for the missing victims, devastated families, and drew national attention.

More than 100 people packed the courtroom Wednesday. Kratz wore a navy blue suit and bright red tie, with makeup covering the tattoos near his ears. His parents sat in the front row. During a break, he turned to smile at and whisper to friends sitting in the front. The victims’ families filled four rows.

The long-awaited trial before County Court Judge Jeffrey L. Finley will be the only time a jury will consider the facts of the case. DiNardo, 22, pleaded guilty to the quadruple murders and was sentenced to four life terms in prison in May 2018. He is in a state prison in Northeastern Pennsylvania.

Kratz, however, turned down at the last minute a plea deal he was poised to accept on the same day DiNardo was sentenced.

Prosecutors have said they will seek the death penalty.

DiNardo lured all four young men to the farm under the pretext of selling them marijuana. He killed Patrick two days before involving Kratz.

Prosecutors say Kratz agreed to kill Finocchiaro as part of a plan. The defense said Kratz didn’t believe DiNardo’s talk of murder, and said DiNardo pressed the gun on him and ordered him to kill Finocchiaro after the three men got to the property.

Kratz weighed 118 pounds at the time and is “not the brightest bulb on the Christmas tree,” with an IQ of 79, Peruto told the jury, saying his client was not equipped to resist DiNardo.

When DiNardo insisted that Kratz kill Finocchiaro, Peruto said, Kratz gave him back the gun and said he couldn’t do it. DiNardo then shot Finocchiaro, Peruto said, turned to his cousin and said, “We’re in this together.”

Prosecutors disputed that, and said Kratz shot Finocchiaro in the head, killing him, before DiNardo took the gun and fired a second shot into the body. They said Kratz bypassed opportunities to escape, call for help, or warn Finocchiaro.

Afterward, prosecutors said, DiNardo picked up Meo and Sturgis, killed them while Kratz kept watch, and solicited his cousin’s help in loading the bodies into a pig roaster, lighting it, digging an over-12-foot hole with a backhoe, and using the backhoe to dump and bury the bodies.

Then, Kohler said, they went to Steve’s Steaks and bought cheesesteaks.

DiNardo later confessed and identified Kratz as his accomplice. DiNardo’s plea deal allowed him to escape the death penalty in exchange for telling investigators where he had buried Patrick’s body separately on the DiNardo property.

Kratz told investigators in 2017 that he didn’t shoot any of the men himself, but he later reportedly told investigators he had participated in the killings because he was afraid of DiNardo. Peruto told the jury that Kratz had been manipulated by his state-appointed lawyer at the time to give a taped confession in exchange for a plea deal.

The testimony also offered a glimpse into the investigation of the boys’ disappearance. Within hours of their families’ calls to police, authorities knew of DiNardo, had visited one of his family’s properties near the farm, and had traced the missing boys’ cell phones to final pings off a nearby cell tower. They were realizing this wasn’t a case of young people running off to the Shore for the weekend, Solebury Police Cpl. Jonathan Koretzky said from the witness stand.

State police, the FBI, and other teams were called in, an aerial search was done, and authorities fanned out over the DiNardo farm.

“The days that follow turn into a manhunt of immense proportions,” Kohler said. “A community … was paralyzed in the search for these boys’ bodies and their killers.”

Law enforcement agents on the witness stand testified that investigators searching the overgrown 105-acre farm found bloodstains and drips on both levels of the barn, the driveway, a ladder, and a sheet, and on the backhoe. The upper-level barn floor had a bullet hole.

Investigators later found Finocchiaro’s cell phone wedged under a piece of plywood in the barn and found two firearms under a floorboard in a horse stall, said Quakertown Detective and Bucks crime scene investigator Matthew Molchan. They also found a cigarette butt with Kratz’s DNA on it.

With the danger of the hole collapsing, a pervasive smell of gasoline, and the need for ventilation, light, and makeshift scaffolding in the cramped hole, it took three days to excavate the metal tank and find the three bodies underneath, FBI Special Agent Michael Byrnes testified.

Before court adjourned, Kratz’s attorneys asked the judge to sequester the jury. Finley denied the motion.

In court Wednesday, as Meo’s mother, Melissa, described his friendship with Sturgis, one woman in the jury wiped her eyes.

“They were really good friends. Inseparable buddies,” Meo said, crying as she briefly testified. “Yin and yang, and peanut butter and jelly. They were wonderful.”