Lowell Man Pleads Guilty in Chelmsford Jet Ski Crash

CHELMSFORD – Middlesex District Attorney Marian Ryan, Massachusetts Environmental Police Majors Patrick Moran and David Loos, and Chelmsford Chief of Police James Spinney have announced that Douglas Dematos, 34, of Lowell has pled guilty to charges in connection with a fatal jet ski crash that took place on August 13, 2017, in Chelmsford.

Mr. Dematos pled guilty Monday in Lowell Superior Court to charges of operating a jet ski while under the influence of alcohol, causing a death. Judge Kathe Tuttman sentenced Dematos to six years to six years and one day in state prison.

At approximately 10:34 p.m., on Sunday, August 13, 2017, Chelmsford Police responded to the Merrimack River for a report of a disturbance. Upon arrival, officers conducted a preliminary investigation and learned that two jet skis had collided on the river and that the female who was riding on the jet ski struck by Dematos had been thrown from the watercraft and was missing. Shortly after 10:00 a.m. on August 14, the body of Isabelle DaSilva, age 16, of Lowell, was recovered from the river. Evidence gathered during the investigation showed that Dematos had been operating the jet ski that struck the rear of the other jet ski being ridden by the female victim and another male. Officers at the scene observed Mr. Dematos to be showing signs of intoxication.  Mr. Dematos’ blood was later tested and determined to be well above the legal limit. 

The investigation in this case was conducted by the Middlesex District Attorney’s Office, the Chelmsford Police Department and Massachusetts Environmental Police. The Chelmsford Fire Department, State Police and the Lowell Police/Fire Dive Team assisted in the recovery efforts.

The prosecutors assigned to this case are Assistant District Attorney Daniel Harren and Assistant District Attorney Ashlee Mastrangelo. The Victim Witness Advocate is Leia Kaplan.