Steven Hayes, standing trial for the deadly 2007 home invasion in Connecticut, admitting to killing at least one of the three female victims, according to testimony heard in a New Haven court today.
Corrections Officer Jeremiah Krob, who has been responsible for the continuous observation of Hayes while he sits in prison, testified today that he has overheard conversations Hayes has had with another inmate, Vernon Cowan, in which he admitted to killing Jennifer Hawke-Petit.
Hawke-Petit and her two daughters, 17-year-old Hayley and 11-year-old Michaela, died during a gruesome invasion of the family's Chesire, Conn., home in July 2007.
Hayes allegedly told Cowan that he didn't know if he could "go through" with killing Petit-Hawke, according to Krob, but when he spotted police cruisers outside the family's home that July day, he did it.
"He never mentioned how he killed Mrs. Petit. He just stated that he did kill Mrs. Petit," Krob testified.
Some of what Krob heard was in conversations between Hayes and other inmates using an inmate communication system.
Krob said Hayes talked with his cell neighbor by placing "empty toilet paper rolls and placing it over the sink drain and talking to each other through that system."
The officer told the court that Hayes had told the other inmate that investigators would find physical evidence of sodomy when they examined his alleged accomplice, Joshua Komisarjevsky. Komisarjevsky, will face a trial of his own at a later date.
"Hayes did mention that Komisarjevsky had taken cell phone pictures of the youngest Petit girl and was trying to e-mail them to his friends," said Krob.
Hayes and Komisarjevsky allegedly tried to cover up their crime by setting the house on fire after tying the girls to their beds.
"Hayes was concerned about being charged with arson. He believes that he couldn't be charged with arson because he had only poured gasoline down the stairs of the Chesire home, not lit the match," said Krob.
The fire allegedly set by the two ex-cons was so ferocious that there was no chance of rescuing the three victims from the flames, according to other expert testimony today.
Paul Makuc of the state fire marshal's office told the jury who will decide the fate of Hayes that the fire that killed the two Petit girls and burned the body of their mother was set "by human hands."
The "ignitable liquid" used to start the fatal fire contained accelerants, helping the flames to travel that much faster through the home, Makuc told the New Haven courtroom. Hayes and his alleged accomplice are accused of pouring the gasoline like substance on the bodies of the Petit daughters and around their beds.
Makuc's said that there was "no carpet left" in the room where Hawke-Petit's body was found, and that "some parts of her body [were] nearly completely consumed by the fire."
Komisarjevsky and Hayes Allegedly Tortured Petit Family Prior to Killing Them
Last week, testimony revealed that Hawke-Petit had been strangled to death after she'd been raped, while Hayley and Michaela died of smoke inhalation.
Makuc said today that the Petit's sun porch seemed to have sustained the heaviest fire damage, and that the blaze was so fierce that investigators could identify only "some strings" of a couch that had been in the room.
Hayes attorney, public defender Thomas J. Ullmann, pressed Makuc on whether his investigation made clear who was responsible for pouring the flammable liquids.
Asked by Ullman whether his "science" told him who poured the gasoline or who "handled the various containers," Makuc responded, "No it does not."
Hayes and Komisarjevsky are accused of torturing the Connecticut family in June 2007 during a brutal home invasion during which they snapped pictures as they sexually assaulted two of their alleged victims, according to testimony heard in court last week.
The prosecution ended its case today. Closing arguments are expected to take place Friday, with the jury being sent into deliberations Monday.
In what has become a continuously heartbreaking and graphic murder trial, computer and technology expert John Farnham was shown eight pictures off Komisarjevsky's cell phone, taken while he and defendant Hayes allegedly brutalized and killed Hawke-Petit and her two daughters.
The jury was spared the shocking images, but Farnham was asked to describe each one. In two, he said, Komisarjevsky -- who will face trial after Hayes -- was photographed nude and posing suggestively. Five showed a young female with her arms tied above her head, with a cloth over her face and a close up of her underwear.
The eighth photo was of an older female, her legs spread.
Dr. William Petit, the lone survivor of the July 2007 home invasion, has grown visibly upset during the trial but has remained composed, occasionally gripping a courtroom railing.
Medical Examiner Wayne Carver has testified that the older of the two Petit girls, Hayley, was found laying face down in the hallway, but that the front of her clothing was more severely burned than the back, indicating she'd been directly exposed to fire.
He speculated that she had managed to free herself after being tied to her bed and made her way down the hallway and that Michaela had likely died a painful death.
The courtroom also heard testimony today regarding a series of text messages that Hayes and Komisarjevsky sent back and forth before allegedly heading out around 3 a.m. to the Petit home, where Komisarjevsky had followed Hawke-Petit from a grocery store.
"I'm chomping at the bit to get started," Hayes wrote to Komisarjevsky at 7:45 p.m. the previous night. "Need a margarita soon."
And then, between 8:45 p.m. and 9:20 p.m., the following exchange:
"We still on?" Hayes sent to Komisarjevsky.
"Yes," Komisarjevsky replied.
"Soon?" Hayes wrote back.
"I'm putting kid to bed," Komisarjevsky then wrote to Hayes. "Hold your horses."
"Dude the horses want to get loose," Hayes replied. "Lol."
Dr. William Petit Left Courtroom During Gruesome Testimony
Throughout much of the trial Hayes has simply sat still and looked forward. He occasionally steals glances around the courtroom, surveying the audience, and he appears to study the exhibits the prosecution has presented.
Last week, jurors heard for the first time an intimate description of exactly what happened the day the Petit family was killed as told by a police officer who said he took Hayes' 70-minute confession.
Detective Anthony Buglione told the court that Hayes said the original plan had been to simply rob the Petit's home, but in the course of the robbery things spiraled out of control.
Buglione testified that he spoke to the suspect hours after Hayes, 47, and Komisarjevsky, 30, allegedly doused the Petit's Cheshire, Conn., home in 2007 with gasoline and set it on fire with Petit's wife and children tied to their beds.
William Petit, who had been beaten and tied up in the basement, barely escaped. Hayes smelled of gasoline and gave his confession without emotion, Buglione said.
At one point during the alleged assault, Hayes took Petit's wife, Jennifer Hawke-Petit, to the bank to withdraw money.
While Hayes was out with Hawke-Petit, Buglione said that, according to Hayes, Komisarjevsky was supposed to put the family in the car and then the pair would burn the house down. When Hayes returned, however, Komisarjevsky told him he had already sexually assaulted Michaela and told Hayes to "square things up" and do the same to the wife, which Hayes allegedly did.
Hayes and Komisarjevsky first crossed paths at a halfway house where the two attended Alcoholics Anonymous meetings, police said. Desperate for money, they hatched the plan after a few drinks.
ABC News' David Muir, Sarah Netter, Lee Ferran and The Associated Press contributed to this report.