Stephen Tanabe, 47, pleaded not guilty to three counts of conspiracy: conspiracy to sell steroids, conspiracy to obstruct justice and conspiracy to falsely arrest.
He also pleaded not guilty to one count of accepting a bribe and three counts involving an assault weapon.
His attorney, Daniel Russo, said outside the Walnut Creek courtroom that Tanabe is innocent.
"I think when all the wash comes out it's going to be shown that Mr. Tanabe did nothing in violation of the law with relation to Mr. Butler and Mr. Wielsch.
Tanabe was charged along with Norman Wielsch, the former commander of the now-suspended Central Contra Costa County Narcotic Enforcement Team, and Christopher Butler, a private investigator, in a 34-count criminal complaint.
All three men are former Antioch police officers.
Wielsch and Butler, both 49, pleaded not guilty in March to charges of conspiracy; selling methamphetamine, marijuana and steroids; and possessing methamphetamine, marijuana and steroids for sale.
They pleaded not guilty again today to an amended complaint that added charges against Tanabe to the case and additional charges against Butler.
Attorneys in the case said Wielsch allegedly stole drugs from law enforcement evidence lockers and Butler arranged to sell them or have them sold.
According to court records, Tanabe was allegedly involved in steroid sales.
Some of the charges against Tanabe and Butler stem from a separate alleged scheme in which Butler hired attractive women to lure men to bars and get them drunk. He would then allegedly call Tanabe and have the men arrested for drunken driving, according to the complaint.
The men in these cases were often the husbands of Butler's clients who were involved in legal battles with their spouses.
Wielsch was not involved in the so-called "dirty DUI" scheme, prosecutors said.
Russo said Tanabe did not know that there was a setup behind the arrests. He said Tanabe received tips from Butler in two cases about men who were extremely intoxicated who were about to get in their cars and drive away.
He followed them until they violated the law and then pulled them over, Russo said.
"The irony is that the people who were stopped on the DUIs were drunk," Russo said. "He was doing his job."
He said that police officers often rely on tips to catch drunken drivers and that there is nothing illegal about that.
"What he got from Mr. Butler were tips," Russo said. "He had no idea about the decoys."
As for allegations that Tanabe took a bribe, Russo said, "That is a flat-out lie."
Russo said he is confident that Tanabe would be exonerated, but said, "regardless of how it comes out, his life has been ruined."
Wielsch's attorney Michael Cardoza has said Wielsch admitted to the charges early on and has been cooperating with the investigation.
Butler's attorney William Gagen said a new twist in the case is the role that a confidential informant played in helping investigators crack the case.
Gagen claimed that the confidential informant "was a very active participant in promoting the efforts of the sale of different types of contraband."
He said the informant also participated in drug sales themselves and benefited from his role as a confidential informant.
As part of the fallout from the alleged scandal, the Contra Costa County District Attorney's Office has dismissed 15 pending criminal cases and declined to file charges in five more cases involving "dirty DUI" arrests, District Attorney Mark Peterson said.
Operations of the Central Contra Costa County Narcotic Enforcement Team have been suspended indefinitely.
All three men are scheduled to return to Contra Costa County Superior Court in Walnut Creek on June 23 to set a date for a preliminary hearing.