Defendant Pleads Not Guilty by Mental Disease or Defect for Killing His Sister

Erie County District Attorney Michael J. Keane announces that Nicholas X. Allen, 26, of Buffalo, entered a plea of not responsible by reason of mental disease or defect, pursuant to Section 220.15 of the New York Criminal Procedure Law, before State Supreme Court Justice Debra Givens. A Grand Jury indicted Allen on four counts for the fatal stabbing of his 17-year-old sister inside their North Buffalo home and his alleged actions immediately after the homicide in May 2025.

Under New York law, a defendant may only enter a plea of not responsible by reason of mental disease or defect to the entire indictment with the consent of the prosecution and the approval of the Court. The Erie County District Attorney's Office conducted a careful review of all evidence, including the facts of the case, psychiatric evaluations, and the opinion of a forensic mental health expert. In consultation with defense counsel, we agreed that the defendant met the legal basis for lack of criminal responsibility at the time of the offense. Our office consented to the plea in the interest of justice. The Court accepted the plea after determining there was a factual basis for this disposition.

The defendant will be committed to the custody of the New York State Office of Mental Health for examination and further court proceedings to determine the appropriate level of confinement, supervision, and treatment. He will remain subject to the jurisdiction of the Court under the procedures pursuant to New York Criminal Procedure Law Section 330.20.
"This case represents an unimaginable tragedy for this family, and my thoughts remain with them as they continue to grieve. While no legal resolution can undo the pain caused by the loss of a loved one, prosecutors have the responsibility to follow the law and pursue justice based on the evidence. We determined that this plea was the most appropriate and just disposition," said DA Mike Keane.

DA Keane commends the Buffalo Police Department for their work in this investigation as well as ECDA victim advocate Kimberly Rapp.

The case is being prosecuted by Assistant District Attorney Justin H. Caldwell of the Homicide Bureau and Assistant District Attorney Rachel Schepart of the Felony Trials Bureau.