A former Brunswick police officer who is facing charges for allegedly assaulting a 17-year-old during a 2025 traffic stop is being sued.
The lawsuit, filed in federal court Friday, names Nathan Day, an additional unnamed officer and the town of Brunswick as defendants.
The filing alleges that Day, 27, used excessive and unprovoked force against the teenage girl, slamming her head into her car and onto the ground and knocking her out, leaving her with severe injuries. It also says Day and the other officer falsely arrested her without cause to believe she had committed a crime.
Day was charged with Class D assault in March. He waived arraignment and has pleaded not guilty to the misdemeanor charge.
Brunswick police Chief Scott Stewart confirmed that Day was no longer with the department Saturday.
The name of the teenager — who is now an adult — is included in the lawsuit. The Portland Press Herald is not identifying her because she was a minor at the time of the alleged assault.
The lawsuit alleges that, on the day of the traffic stop, officers pulled over the teen’s boyfriend in the parking lot of the Cook’s Corner shopping plaza. She had been following him in a separate car while they were driving to a body shop to repair a taillight on his vehicle, and she followed her him into the parking lot when he was pulled over.
The filing says the then-17-year-old was waiting across the parking lot when Day ordered her out of her vehicle and assaulted her, knocking her unconscious.
Officers arrested her for traffic violations that were dismissed in September. She was brought to the hospital in handcuffs. She suffered a head wound that required staples, a concussion and foot fractures, and she experienced seizures, the lawsuit alleges.
In an email Friday, Day’s attorney, Marc Beaudoin, denied the allegations outlined in the complaint and detailed a different narrative of the arrest.
Beaudoin said that, while in the parking lot, Day asked the teenager multiple times to come over to him, intending to give her a ticket for using her cellphone while driving. When she refused, Day approached and began to handcuff her, at which point she attempted to move away from him and kicked him in the knee, Beaudoin said.
Day “did not use any excessive force” during the arrest, Beaudoin said, and the teen’s injuries were “inadvertent and due to her own refusal to comply.”
The teen’s lawsuit also cites multiple instances in which Day was disciplined by the department.
According to department records obtained through a public records request this year, Day was formally disciplined three times before the alleged assault — in September 2023, July 2025 and August 2025.
In the August 2025 incident, Day was disciplined and required to complete remedial training after reportedly tackling a suspect. The other two disciplinary reports involve Day driving a police cruiser and pursuing another vehicle in ways that violated department policy.
The suit accuses the town of failing to properly discipline Day for his “escalating misconduct,” and of demonstrating a broader pattern of deliberate indifference toward reports of officer misconduct.
“While Nathan Day’s actions last December are at the heart of this suit, this case is also about the lack of discipline in the Town of Brunswick’s police department, which allowed Mr. Day to stay on the force despite repeated flouting of the Constitution and departmental regulations,” attorneys representing the plaintiff said in a joint statement Friday.
The plaintiff is seeking compensatory and punitive damages, plus attorney’s fees, and has requested a jury trial.
This story was originally published by the Maine Trust for Local News. Katie Langley can be reached at klangley@metln.org
Portland Press Herald Staff Writer Drew Johnson contributed to this report.