In Pleasantville, Boris Lainez-Rosales admitted killing Leslianette Quintana-Betancourt after investigators challenged his account of an accidental fall.
MAYS LANDING, N.J. — Blood evidence, bleach odors and a baseball bat found outside a Pleasantville home helped turn a reported stair fall into a murder case, authorities said.
Boris Lainez-Rosales, 28, has pleaded guilty to first-degree murder in the death of Leslianette Quintana-Betancourt, 25, his pregnant domestic partner. Prosecutors said he admitted beating her with a baseball bat on Dec. 2, 2024, then staging the home to make her death appear accidental.
The case began with a claim that Quintana-Betancourt had fallen down a staircase. Lainez-Rosales called 911 around 2 a.m. Dec. 3 and said she was unresponsive after falling down about 12 steps. Police found her at the bottom of the stairs. That account gave investigators an immediate question: Did the injuries and the scene match a fall? Court records later showed that investigators believed they did not. The home became a layered crime scene, with the stairwell, basement, backyard and car each carrying a different piece of the state’s case.
The stairwell raised early doubts. Police said there were no blood stains in and around the stairs, even though Quintana-Betancourt had suffered multiple blunt-force injuries. Investigators also said her body smelled of bleach. Lainez-Rosales had cuts on his hands when police spoke with him, according to the affidavit cited in the case. He told officers she had fallen and that he had called police afterward. The condition of the stairwell did not prove what happened by itself, but it gave investigators reason to search for another location inside the home where the injuries may have been inflicted.
That search led to the basement living area. Investigators said they found bloodstains throughout the space and on the walls. They also reported a bleach smell through the apartment and evidence that someone had tried to clean biological material. Prosecutors later said Quintana-Betancourt was dragged from the basement and left near the stairs. The alleged cleanup became important because Lainez-Rosales was initially accused not only of murder but also of tampering with evidence and possessing a weapon for an unlawful purpose. The final plea resolved the murder count and confirmed his admission to the fatal assault.
Investigators then found the weapon they said fit the injuries and the later admission. A baseball bat with bloodstains was recovered in the backyard. Police also found a trash bag in Lainez-Rosales’ car with possible hair attached. The affidavit did not make public every forensic test result, and officials have not released a full evidence inventory. Still, the items described in court records matched the prosecution theory: Quintana-Betancourt was beaten, the scene was cleaned, and the body was placed near the stairway to support a false report to police.
The timeline also mattered. A witness inside the home heard Lainez-Rosales and Quintana-Betancourt arguing from about 9:30 p.m. to 11 p.m. on Dec. 2, according to the affidavit. When the witness went downstairs, Lainez-Rosales escorted the person back upstairs and said everything was fine. A short time later, he came upstairs and used the witness’s phone to call 911. That detail gave investigators a witness-backed window before the emergency call and placed Lainez-Rosales between the argument and the report of a fall.
The injuries described by authorities were not limited to the head. Police said Quintana-Betancourt had blunt-force injuries to her face, arms and abdomen. She had a ruptured placenta, and her unborn child did not survive. Those facts shaped the seriousness of the case and the charge that followed. Lainez-Rosales was indicted in February 2025. The prosecution’s public statements did not describe a motive or explain what the argument was about. The available record also does not say whether any prior domestic incidents had been reported at the home.
The guilty plea came May 19, 2026. In the plea, Lainez-Rosales admitted that he assaulted Quintana-Betancourt, who was pregnant, with a baseball bat at his Pleasantville home and caused her death. The Atlantic County Prosecutor’s Office said the plea calls for 30 years in New Jersey State Prison without parole. The investigation was conducted by Pleasantville police and the prosecutor’s Major Crimes Unit. Executive Assistant Prosecutor Rick McKelvey represents the state, and sentencing is set before Superior Court Judge Joseph A. Levin.
Quintana-Betancourt’s public memorial described her as a beloved sister, daughter, aunt and friend. A friend wrote that she had been happy about becoming a mother. The memorial added a human record to a case otherwise told through forensic details, charges and court dates. It also underscored the two deaths at the center of the case: Quintana-Betancourt and her unborn child. Prosecutors have not announced any separate public proceeding tied to the pregnancy beyond the murder case against Lainez-Rosales.
The case now rests on his guilty plea, the state’s recommended 30-year prison term and the judge’s final sentence. Lainez-Rosales is scheduled to be sentenced July 31, 2026.
Author note: Last updated June 21, 2026.