A law enforcement whistle-blower who told investigators he witnessed a Contra Costa County sheriff's deputy conduct a "dirty DUI" arrest has been relieved from duty in what he said was retaliation for breaking the police code of silence.

William Howard of Danville worked as a reserve in the Sheriff's Department for 19 years until he was dismissed Tuesday without explanation and ordered to turn in his uniform and weapon.

A department spokesman, Jimmy Lee, described Howard's release as an internal matter and declined to discuss it. Reserves are "at will" employees and are subject to dismissal without cause, according to California state law.

Howard told The Chronicle he was ostracized by fellow officers, chided by commanders and removed from prime assignments in the months after he cooperated with internal affairs investigators who were building a criminal case against former Deputy Sheriff Stephen Tanabe, 49.

"I knew I was doing the right thing," Howard said. "But I didn't anticipate the extent of anger that would be directed toward me."

Howard's Feb.23, 2011, statement played a critical role into the investigation of Tanabe, an associate of private investigator Christopher Butler, 50, of Antioch.

A federal grand jury later indicted Butler and Tanabe on conspiracy charges alleging they worked in cahoots to arrest three men Butler had targeted on behalf of his clients - the ex-wives of the targeted men.

Butler was allegedly paid by the women to carry out the "dirty DUIs" (drunken-driving arrests) to sully the men with criminal records for pending divorce and custody battles.

In May, Butler pleaded guilty to the conspiracy charge, as well as additional drug charges, and remains in federal prison in Dublin as he awaits sentencing next month. A judge dropped another count that accused him of compensating Tanabe with cocaine and a pistol for taking part in the arrests.

Tanabe has pleaded not guilty and remains free on bail.

Volunteer reservists

The Sheriff's Department uses about 60 volunteer reservists. All are certified peace officers and are allowed to perform duties of varying responsibility to assist full-time officers. As a part-time reserve deputy, Howard earned $15,000 to $20,000 each year in per diem salary and was covered by the department's health insurance for injuries suffered on the job.

A Navy veteran, Howard carried a department-issued weapon, worked court security and was regularly assigned to the Marine Patrol unit.

He joined the sheriff's office after retiring from a career as a construction executive and overcoming a bout with colon cancer.

"After surviving cancer, being a reserve deputy was an important and significant way for me to strengthen my community," he said. "I took on a lot of responsibility and worked every task I was assigned no matter how dangerous, difficult or unpleasant."

In return, he received numerous letters of commendation and pointed to several year's worth of quarterly evaluations where supervisors consistently awarded him the highest marks and noted his professionalism and positive attitude toward the job.

On patrol in Danville

On Jan. 14, 2011, Howard was partnered to ride with Tanabe and patrol Danville.

In an affidavit, Howard told investigators he heard Tanabe make eight to 10 phone calls on his cell phone to a person Tanabe referred to as "my p.i. friend."

Howard told investigators it appeared Tanabe was receiving updates about a targeted individual from the friend.

Tanabe eventually pulled over Mitchell Katz, a Livermore winemaker, moments after Katz drove away from the Vine wine bar on Hartz Avenue.

After Katz was booked on suspicion of drunken driving, Tanabe and Howard returned to patrol. Howard told investigators Tanabe then confessed the arrest was a "set up" and that Tanabe had used the term "dirty DUI" to describe the incident.

Howard told The Chronicle the events leading to Katz's apprehension and during his jailing raised some red flags, yet he did not suspect he was in the midst of what federal prosecutors later described as an "elaborate ruse."

"I had no reason to think he shouldn't be given the benefit of the doubt," Howard said of the more experienced deputy. "I wondered if I might be learning something different, and it would all come into focus, because it always had in the past."

Stashing a bag

Four weeks later, on Feb. 16, after Butler's arrest was splashed across the news, Howard told investigators Tanabe showed up at his home in an agitated state and revealed his "p.i. friend" was Butler. Howard also said the deputy feared police would search his home and handed the reserve deputy a black plastic bag to stash in his attic.

Howard said he lost sleep the first night he had the bag, then decided to turn it over to his commanding officer. The bag contained an assault rifle.

After Howard's name was revealed in a search warrant and affidavit issued for Tanabe's arrest, he said his life in the department took a turn for the worse.

In a meeting he believes was designed to intimidate him, Howard said one commander told him, "If you were a regular I would have fired your ass."

Another officer who broached the DUI scandal allegedly told Howard, "I knew Tanabe and I liked him. And I don't know you at all."

Howard said he was removed him from Marine Patrol and assigned to the civil unit to assist with foreclosure notices and evictions - the "Siberia" of the department.

On April 12, Howard met with Sheriff David Livingston and said he complained about the disparaging treatment. He said he hoped the county's top law enforcement official would spread the word that Howard should be thanked instead of criticized.

"That was pretty naive of me," Howard said. "He told me to get a thicker skin."

Livingston said of the exchange, "Because it is a confidential matter, I cannot comment even as it applies to a former volunteer."

Howard said while he had no regrets about coming forward, he did regret the negative publicity the scandal had hoisted upon the department.

"Not every cop is corrupt," Howard said. "But you know what, I know why a lot of cops don't speak up - because the system punishes them."