The Oxnard Police Chief John Crombach said the victim's mother reported the crime, accusing 43-year-old senior officer Martin Polo of the crime. The parents are suing Polo and the city for $10 million.
Click in the Eyewitness News Story Window above to watch Jovana Lara's report from the scene.
His partner Frank Brisslinger, 41, is accused of misconduct and misbehavior while on duty.
Both are on paid leave, but Crombach insists the allegations are being taken seriously.
"We initiated the investigation, we provided that to the D.A. for prosecution, and as these other administrative issues came up, we vigorously investigate those as well, so if there's truly the misconduct as alleged then these people will be held accountable. I can guarantee you that," Crombach said.
Polo is a 20-year veteran in the department.
Meanwhile, the department struggles to overcome what they call a serious black mark.
The 12-year-old girl is reportedly being treated at a Utah hospital for teens with emotional problems.
The D.A.'s Office is expected to make a decision on whether to file criminal charges against Polo within the next 30 to 60 days.