By Richard Weizel

MILFORD, Conn. (Reuters) - A Connecticut man pleaded guilty on Tuesday to first-degree abuse and cruelty for keeping his mentally ill sister locked away for years in a padlocked room in her own urine and feces.

Arthur Gauvin, 59, of Seymour, Connecticut, faces up to 10 years in prison for keeping his 57-year-old sister, Nancy Gauvin, in a room police described as a "dungeon" in his home. He will be sentenced by a judge in Superior Court in Milford on July 9.

Before Tuesday's plea, Gauvin was also facing felony charges, including assault and kidnapping, that would have carried longer prison times had he been convicted. Dan Ford, Gauvin’s lawyer, said he will seek five years of incarceration.

Officers found Nancy Gauvin in April 2014 covered in urine and feces inside a bedroom with an odor so strong they could not breathe, according to court documents. Police found her after a complaint from one of the neighbors, who told investigators they believed the woman had been locked away for years.

Police said Arthur Gauvin, who was later arrested, told them he kept his sister there so his dog would not eat her food.

According to probate court records, Nancy Gauvin required "multiple baths and showers" after her arrival at Yale New-Haven Hospital, her hair was matted and her fingernails and toenails about 4 inches long.

Probate records describe her as suffering from a cognitive disorder, "possibly arising from" dementia, a mood disorder, depression or post-traumatic stress disorder. Nancy Gauvin is now living in a rehabilitation facility.

Gauvin is free on $125,000 bond until sentencing, but has been ordered by a judge to stay out of the Seymour home.

(Editing by Richard Valdmanis and Dan Grebler)