Boris Lainez-Rosales is scheduled to be sentenced July 31 in Atlantic County Superior Court.

MAYS LANDING, N.J. — A Pleasantville man admitted in court that he beat his pregnant live-in partner to death with a baseball bat, ending a murder case built around a staged fall claim, prosecutors said.

Boris Lainez-Rosales, 28, pleaded guilty May 19 to first-degree murder in the death of Leslianette Quintana-Betancourt, 25. The plea calls for a recommended sentence of 30 years in New Jersey State Prison without parole. The case now moves toward a July 31 sentencing before Superior Court Judge Joseph A. Levin.

The Atlantic County Prosecutor’s Office said Lainez-Rosales admitted that he assaulted Quintana-Betancourt on Dec. 2, 2024, at their Pleasantville home. She was his domestic partner and was pregnant at the time. Executive Assistant Prosecutor Rick McKelvey represents the state. The investigation was handled by the Pleasantville Police Department and the prosecutor’s Major Crimes Unit. The plea resolved the central murder charge more than a year and a half after the killing, leaving the court to decide whether to impose the sentence recommended in the plea agreement.

The first public account from Lainez-Rosales was not a confession. Investigators said he called 911 around 2 a.m. Dec. 3 and told authorities that Quintana-Betancourt had fallen down about 12 stairs and was unresponsive. Officers and first responders arrived and found her at the bottom of the staircase. The scene first appeared to be framed as a fall inside the home, but police later said key details did not match that account. The injuries, the condition of the stairwell and later findings in the home shifted the case from an emergency call to a homicide investigation.

An affidavit cited in court records described a witness inside the home who heard Lainez-Rosales and Quintana-Betancourt arguing from about 9:30 p.m. to 11 p.m. on Dec. 2. The witness went downstairs to check on the noise and was escorted back upstairs by Lainez-Rosales, who said everything was fine. A short time later, the affidavit said, Lainez-Rosales went upstairs to the main living area and used the witness’s phone to call 911. That timeline became a key part of the case because it placed the couple together during a long argument before the emergency call.

Police said Quintana-Betancourt suffered blunt-force injuries to her face, arms and abdomen. Investigators also reported that she had a ruptured placenta and that her unborn child did not survive. The affidavit said there were no blood stains in and around the stairwell, even though her body was found there. Police said her body smelled of bleach. Officers also noted cuts on Lainez-Rosales’ hands when they spoke with him after he claimed she had fallen. The cause and pattern of injuries led investigators away from the stair-fall account and toward an assault allegation.

A search of the home added more evidence. Investigators said they found bloodstains throughout the couple’s basement living area and on the walls. They also detected the smell of bleach in the apartment and found signs of attempts to clean biological evidence. Police found a baseball bat in the backyard with bloodstains on it, according to the affidavit. They also recovered a trash bag from Lainez-Rosales’ car that had possible hair attached. Those findings helped prosecutors argue that the fall story was staged after the attack.

Lainez-Rosales was indicted in February 2025 on charges tied to Quintana-Betancourt’s death. Local coverage of the case said he was initially charged with murder, tampering with evidence and possession of a weapon for an unlawful purpose. The guilty plea to first-degree murder means prosecutors no longer need to prove the case at trial. It also means Lainez-Rosales admitted in open court that the fatal assault happened with a bat inside the Pleasantville home. The plea agreement does not erase the judge’s role at sentencing, but it gives the court a recommended prison term.

Quintana-Betancourt was remembered by friends and family as a sister, daughter, aunt and friend who was preparing for motherhood. In an online tribute, a friend wrote that she had been happy about becoming a mother and starting a new journey. The tribute described her as kind and said her laugh and smile could brighten a room. Those words became part of the public record of the case as the legal filings focused on the killing and the attempted cover story.

The case stands at the sentencing stage. Lainez-Rosales remains set for a July 31 hearing before Judge Levin, where prosecutors are expected to seek 30 years in state prison without parole under the plea agreement.

Author note: Last updated June 21, 2026.