(Updates with Cowley surrender, lawyer's quote)
By Jennifer Dobner
SALT LAKE CITY, June 19 (Reuters) - Prosecutors charged a former Utah police detective with manslaughter on Thursday in the shooting death of a woman during a botched undercover drug operation in 2012, authorities said.
Former West Valley City police officer Shaun D. Cowley, 34, faces a single count of second-degree felony manslaughter in Salt Lake City's district court.
He surrendered to authorities Thursday and was booked and released, his lawyer said. If convicted, could face up to 15 years in state prison.
The charges came nearly 18 months after Danielle Willard, 21, was shot in the head as she sat in her car in an apartment complex parking lot, and almost a year after the Salt Lake County District Attorney's Office ruled that the shooting was not justified.
Cowley was dismissed from the police force last year.
Charging documents say he and another officer were watching a suspected drug house on Nov. 2, 2012, when they saw Willard conducting what they believed to be a narcotics deal in her car.
When officers approached, she tried to drive away, and Cowley opened fire after she refused his orders to stop and get out of the car.
An investigation found Willard was hit through the driver's side window, and that Cowley was beside the car - not in front of it and at risk of being run over, as he had previously said.
Charging documents said his actions "contradicted police use of force standards" and were unjustified because he had not been faced with imminent "threat of death or serious bodily injury."
"Defendant acted recklessly," the documents said.
Cowley's attorney, Lindsay Jarvis, said in a statement that prosecutors relied on "manipulated evidence."
"We are confident that Detective Cowley will prevail at trial," Jarvis said.
The investigation uncovered numerous problems, including corruption and mishandling of evidence, in the now-disbanded drug unit, prompting state and federal prosecutors to toss out more than 120 of the department's cases.
Willard's relatives and others have protested the handling of the case and questioned why it was taking so long. District Attorney Sim Gill said the probe was rigorous.
"Nothing about this investigation has been ordinary," he said on Thursday.
Willard's family is satisfied with the manslaughter charge, their Los Angeles-based attorney Mark Geragos told Reuters.
"It's a milestone in our quest for justice for Danielle," he said "We're hopeful that the truth will now come out." (Reporting by Jennifer Dobner; Editing by Daniel Wallis, Gunna Dickson and Bill Trott)