Three more defendants pleaded guilty Friday in the federal case that rocked the Henry County Sheriff's Office, including a former canine handler and a woman who had an affair with the case's key informant.

Ginger Lewis, 28, of Martinsville was accused of trying to sell drugs for James Alden Vaught, who was then a sergeant for the sheriff's office and is now the government's star witness in the case, prosecutors say.

Lewis was indicted in October along with six other civilians and 13 current and former deputies. Former Sheriff Frank Cassell was accused of obstructing the federal investigation.

Lewis pleaded guilty to one count of possession with intent to distribute the sedative ketamine, also known as a date rape drug.

According to prosecutors, Vaught wanted to get rid of the drugs after agents arrested William Reed, a civilian who rented a house from Vaught.

Reed, who has pleaded guilty to conspiracy, told investigators that the house was used as a drug drop and a place for some Henry County sheriff's deputies to have extramarital affairs, court documents show. He said he paid Vaught in cash and ketamine to use the house.

Lewis reportedly tried to sell the ketamine but had no luck because a buyer feared she was working for the government. Police recovered 32 vials of the drug from Lewis during the investigation.

Walter Hairston, 35, of Bassett admitted Friday to being part of a racketeering conspiracy.

Officials say Hairston, who was a canine handler for the department, took drugs intended for dog training purposes and gave them to Vaught to sell. This allegedly happened at least 10 times.

In August 2005, Hairston and Vaught were caught on tape agreeing to deny the illegal activity.

Also on Friday, truck driver Mark Anthony Roberson, 48, of Martinsville pleaded guilty to possession of a firearm with an obliterated serial number.

Roberson bought the gun at an estate sale and later noticed the serial number had been erased, said assistant U.S. Attorney Andrew Bassford.

But instead of notifying the authorities, Roberson traded the gun's receiver, where the serial number is typically found, with a receiver owned by co-defendant Travis Todd Wilkins, a former deputy who pleaded guilty Wednesday.

Unbeknownst to Roberson, Wilkins planned to build a fully automatic gun with the part, Bassford said.

Lewis and Hairston face up to 20 years in prison; Roberson could get up to five.

Thirteen defendants in the case have now pleaded guilty, leaving seven more to either plead or stand trial.