Sheriff’s deputies in Iowa erred when they did not investigate a neighboring county prosecutor for drunk driving after encountering her intoxicated in her car on the side of a highway late one night in 2019, a state investigation has concluded.

Critics have long questioned whether assistant Jackson County Attorney Amanda Lassance received special treatment in the incident, which began when her then-boyfriend called 911 to report she had hit him during the drive home from a night out and was now in a car parked along Highway 61.

But findings released Thursday by the Office of Ombudsman, a state agency that investigates complaints against government officials, found no indication that officers gave Lassance a pass because of her law enforcement job. Instead, the probe found Clinton County deputies should have conducted an OWI investigation but did not do so because of a misunderstanding of the law, driven by inexperience and inadequate training and supervision.

Responding deputies found Lassance, who routinely prosecutes OWI cases, domestic abuse and other crime, in the driver’s seat with blood-shot eyes, slurring her speech and empty beer cans strewn throughout her vehicle. Lassance said that she had been drinking beer — but claimed she started only after stopping her car along the highway.

Deputies never ordered her to conduct field sobriety tests or asked her to take a breathalyzer to determine her blood alcohol level. They also did not find any cause for a domestic violence arrest, saying they found no evidence her boyfriend was injured.

Instead, they cited her for an open container violation for which she later paid a $335 fine and ultimately drove her back to near her office at the Jackson County Courthouse in Maquoketa. Another deputy drove her back to pick up her car the next day.

The investigation by senior assistant ombudsman Bert Dalmer found that deputies erroneously believed they could not charge Lassance with operating while intoxicated because her car was shut off when they found her. Deputies also mistakenly thought they could not conduct a field-sobriety test since her keys were not in the ignition, he found.

Clinton County Attorney Mike Wolf said in a press release Thursday that he agreed that the evidence at the scene “provided reasonable cause to further the OWI investigation.”

Clinton County Sheriff Bill Greenwalt’s office said the deputies on the scene would have benefited from the ability to contact a supervisor for guidance, saying they were on their own to “resolve many urgent issues presented on a dark roadside out in the country.”

The office pledged to improve training for deputies on OWI cases, increase supervision within the patrol division and improve its recording equipment.

Dalmer said Friday that he could not hear the conversation between Lassance and a deputy outside of her vehicle because audio on a dash-camera video was drowned out by interference from his squad car’s lights.

But he said his review found the deputy was not influenced by Lassance's title or connections to law enforcement, noting the officer acted professionally and wrote a thorough report.

“I attribute his errors to a relative lack of experience on OWI stops and insufficient supervision and training, which are easily addressed moving forward,” Dalmer said.

The incident occurred near the Clinton-Jackson county line, and deputies from both departments responded to the call. Jackson County deputies, who work closely with Lassance, stepped back after learning they were in a neighboring county.

Dalmer said his investigation concluded Jackson County deputies should have written a report of the incident, and the Jackson County sheriff agreed.

The case was brought to light through dogged reporting by local newspapers, including the Maquoketa Sentinel-Press. A judge had granted the newspaper's request for the release of squad car and body camera footage related to the incident last year.

Lassance, 39, didn't return messages seeking comment.