The former second-in-command at the Denver Sheriff Department has been fired for giving preferential treatment to a department captain who faced criminal charges.

Frank Gale, who once oversaw the Downtown Detention Center and served as the department’s spokesman, on Wednesday was given a termination letter, which was obtained by The Denver Post.

The dismissal triggered a stern response from the Fraternal Order of Police, where Gale holds a national office and which represents Denver sheriff’s deputies in collective bargaining negotiations with the city.

He is the third high-ranking Denver sheriff’s officer to be fired or demoted in the past year.

DOCUMENT: Read Frank Gale’s disciplinary letter.

Gale’s firing is the third time he has been terminated by the sheriff’s department. He was fired in 1991 and 2000, and each case involved allegations of assaulting an inmate, intimidating deputy witnesses and dishonesty. In both cases, he appealed the decision and was reinstated, according to his latest termination letter.

He also was one of the most decorated officers in the department, having received the Medal of Valor, a Medal of Merit and two lifesaving medals.

Gale’s most recent problems began in June when one department captain filed a complaint accusing the former division chief of giving preferential treatment to a captain who had been charged in a domestic violence case.

Gale was placed on paid investigatory leave in June after the complaint was made and remained there until his termination on Wednesday.

Capt. Sonja Gillespie was accused of throwing a cell phone at a man during an argument. Her criminal charges were later dismissed, said Daelene Mix, a spokeswoman for the Denver Department of Public Safety.

The sheriff’s department’s internal affairs bureau also investigated whether Gillespie solicited preferential treatment, but those allegations were not sustained, Mix said.

Gillespie has returned to her duties as a captain at the department.

Gillespie is the ex-wife of former Sheriff Gary Wilson, who had given an order that her arrest be treated as any other and then recused himself from further action regarding her arrest or disciplinary proceedings. That left Gale as the highest-ranking officer to deal with the situation.

Gillespie was allowed to wear her civilian clothes to her arraignment rather than her jail jumpsuit, which contradicts the jail’s protocol.

Gale attended the entire hearing and then allowed her to leave through the courthouse’s front doors rather than making her go through the department’s normal release procedures, according to his disciplinary letter.

Two deputies were waiting with a car and drove Gillespie away, the letter said.

Gillespie had not filled out the necessary paperwork for her personal recognizance bond or registered with pre-trial services. She had to return to the downtown jail to do so.

Throughout the internal investigation, Gale repeatedly said he did not order deputies to release Gillespie through the front door. However, statements from other deputies and video footage from the courthouse indicated that Gale was lying, the letter said.

Because Gillespie’s arrest attracted media attention and was being watched by other department employees, it was crucial that she be treated as any other inmate, the letter said.

“The lackadaisical attitude displayed by Chief Gale and willingness to place the blame at the feet of a relatively inexperienced sergeant brought disrepute on and compromised the integrity of the Department, as well as constituted conduct unbecoming a leader in the Department,” the letter said.

Gale will appeal his dismissal, said his attorney, Don Sisson.

On Thursday, Sisson also threatened to sue the city over a First Amendment violation, saying Gale’s termination was retaliation for his high-profile position in the deputies’ union.

He has spoken up for deputies accused in excessive-force cases and has been critical of efforts to reform the department, Sisson said.

Gale is on the national Fraternal Order of Police union board and is the most powerful voice in the union statewide and one of the most powerful voices for police unions in the country, Sisson said.

The Colorado FOP on Thursday called Gale’s firing an attack on the entire body by Mayor Michael Hancock and Stephanie O’Malley, the executive director of the Department of Public Safety.

“The firing of Frank Gale is union busting designed to send a message to the FOP that is intended to have a chilling effect on its members,” said Mike Violette, executive director of the state lodge. “It is clear this City Administration is determined to weaken or destroy this union and run roughshod over its members.”

But in an e-mail sent through her spokeswoman, O’Malley said the department’s policies support termination for Gale.

“A high standard of professionalism and integrity is expected from members of the Denver Sheriff Department,” the e-mail said. “In those instances where any member of the department is found to depart from the truth, a sacred trust is broken, particularly in an agency whose guiding principles include honesty, personal leadership, integrity and accountability.”

Tension already was high between the administration, which is pushing a massive reform of the department, and the rank-and-file, who have argued that city officials are too quick to condemn them in use-of-force cases.

Also, contract negotiations between the sides reached an impasse during the fall. They are scheduled for arbitration in February.

The department has been under fire for most of 2014 for a series of excessive-force cases, including two that eventually resulted in the city paying millions in settlements to former inmates and in legal fees.

The Gillespie arrest and accusations against Gale furthered the department’s embarrassment.

Hancock and O’ Malley have vowed to reform the department and have hired two national consulting firms to offer recommendations and help find a new sheriff.

Many of the department’s troubles have been tied to the Downtown Detention Center, including failures among its leadership.

Former division chief Michael Than resigned in December 2013 after being charged with stealing tax software from Target. He was sentenced earlier this month to two months in jail.

Wilson stepped down in July after a string of excessive force cases and lawsuits. He now serves as a chief in charge of creating new technology programs for the department.

Noelle Phillips: 303-954-1661, nphillips@denverpost.com or twitter.com/Noelle_Phillips