Cook County prosecutors have flipped a key witness in the grisly murder case of a Logan Square woman who was found nearly decapitated and stuffed into a duffel bag last summer.
Prosecutors have agreed to drop their case against Peter Mathes, who was accused of helping Genesis Silva conceal the murder of Silva’s girlfriend, Brittany Battagalia, in return for Mathes’ testimony against Silva, court records show.
The agreement, filed earlier this month, states that Mathes provided testimony against Silva before a grand jury in January and has agreed to help the state’s attorney’s office in its prosecution of Silva.
On Thursday, Judge Mary Brosnahan agreed to remove Mathes from electronic monitoring, which he had been placed on pending trial when he was first charged in October. Mathes’ motion to reevaluate the conditions of his release was filed on Feb. 7 and cited his agreement to help prosecutors.
“In exchange for full cooperation in the prosecution of Genesis Silva related to the murder of Brittney Battaglia, which occurred between June 2, 2023, and June 3, 2023, and truthful testimony relating to the same matter, the Cook County state’s attorney’s office agrees to dismiss the charges related to Peter Mathes’s pending cases,” the filing states.
His attorney did not respond to a request for comment, and a spokesperson for the state’s attorney’s office declined to comment, citing pending litigation.
The agreement was reached just days after prosecutors announced they were upgrading charges against Silva to first-degree murder, according to court records.
Silva was to go on trial late last month on charges of concealing a homicidal death and possession of a weapon by a felon. Then, days before jury selection, prosecutors announced they would be charging Silva with Battaglia’s murder in a new case, essentially starting the process over.
Prosecutors cited alleged admissions Silva made in recorded phone calls while he was being held at the Cook County Jail awaiting trial, including that Mathes had helped clean up the crime scene. Silva has pleaded not guilty to the earlier charges and in the new case.
Battaglia’s body was discovered during a search of Silva’s apartment in the 2000 block of North Kimball Avenue, police said. She was last seen days earlier after heading there from her home a block away.
An autopsy found she had been stabbed and slashed repeatedly with a sharp object, including a fatal injury to her neck that nearly decapitated her.
Battaglia had been reported missing when she failed to show up at a party and could not be reached by her family.
While investigating her disappearance, detectives conducted a traffic stop on Silva, who agreed to return to his apartment with detectives, where they discovered a large duffel bag in his bedroom, prosecutors said.
The detectives declared the apartment a suspected crime scene, and Silva was told to stay away. When he allegedly tried to sneak inside through a back stairway, Silva was taken into custody, prosecutors said.
A search warrant was obtained and detectives found Battaglia’s body in the duffel bag, as well as a tarp and garbage bags laid out in the kitchen, cleaning supplies and a paint suit, prosecutors said.
Two cellphones, two small pocketknives and an ice pick were also found during a search, prosecutors said. A machete was allegedly found in Silva’s backpack and a second machete was found in his car.
Sources told the Sun-Times that police asked the state’s attorney’s office to approve a murder charge against Silva at the time, but the office initially rejected the charges in favor of charging Silva only with concealing Battaglia’s death and weapons offenses.
Prosecutors have said that a 2009 conviction for sexual abuse bars Silva from possessing a machete. In that case, Silva pleaded guilty in exchange for prosecutors dropping a more serious attempted murder and criminal sexual assault charges. Silva was also required to register as a sex offender.
Months after Battaglia’s body was found, Mathes was charged with concealing a homicidal death and ordered released on electronic monitoring.
At Mathes’ initial appearance, an assistant public defender said that the defendant had no criminal background prior to being charged in the case and had appeared in court after being released by police.
“I recognize that Mr. Mathes has no previous criminal history; however, according to this proffer, his actions appear to have been instrumental in providing items and attempting to dispose of, or disposing of this murdered victim, this murdered young woman,” Judge Susana Ortiz said at the time, according to a transcript of the proceeding.
Ortiz said that she considered Mathes to be a danger to the community, but agreed the risk that his release could pose would be mitigated with electronic monitoring.
“It appears that Mr. Mathes was willing to be a significant participant in the concealment of the body of this murdered young woman,” the judge said. “And it is based upon that that I find that the least restrictive condition would be placing him on electronic monitoring.”
