MOUNT VERNON — Prosecutors filed additional charges Wednesday against Larry and Carri Williams, the Skagit County couple accused of killing their adopted teen daughter Hana Williams last year.

A charge of first-degree manslaughter by domestic violence was added to each of their existing charges.

The couple already is charged with homicide by abuse for Hana Williams' death and first-degree child assault for their treatment of their adopted son.

The charging documents also say aggravating factors in the manslaughter are that the "offense was part of an ongoing pattern of psychological, physical, or sexual abuse of a victim or multiple victims manifested by multiple incidents over a prolonged period of time."

The accusation details that the offense occurred within sight or sound of minor children under 18 — in this case the Williams' other biological children — and that the offense resulted in "deliberate cruelty or intimidation" of the victim.

Hana was found unconscious in her parents' backyard outside Sedro-Woolley on a rainy night in May 2011.

She was later determined to have died of hypothermia brought on by malnutrition.

Investigative records allege systematic abuse inflicted on Hana and her brother that included starvation, assault and extended periods of time left outside or in small spaces.

Skagit County Prosecutor Rich Weyrich said the new charges wouldn't add time to the Williams' sentence if they're convicted, but "gives us more options."

Larry and Carri Williams are scheduled to be arraigned on the manslaughter charges Nov. 28.