(CBS) — If more cops were prosecuted when misconduct occurs, it would help clean up the Chicago Police Department, critics say.

The Better Government Association and 2 Investigator Pam Zekman examine a case that raises lots of questions about what can happen when a cop even admits to misconduct.

Dashcam video shows the police chase and arrest of 36-year old Ranceallen Hankerson, who was charged with 29 felony counts, including attempted murder and armed robbery for a liquor store stick up.

In a dashcam recording of Officer Allyson Bogdalek calling a colleague, she can be heard saying: “We did a photo array. He couldn’t he couldn’t pick him out of the pictures that we gave him.”

That’s information that could have helped Hankerson’s defense, but officer Bogdalek later testified under oath during a pre-trial motion hearing she never showed the victim the photo array.

“It was immediately apparent that Bogdalek had lied because the video where she discusses the photo array was played in open court,” civil-rights attorney Jared Kosoglad says.

Just before the trial, Bogdalek admitted to an assistant state’s attorney she had lied about the photo lineup. The charges against Hankerson were dropped.

“If a police officer lies in a criminal case then the potential criminals are allowed to go free,”  Kosoglad says.

According to records outlining a subsequent perjury investigation by the Cook County State’s Attorney’s Office, Officer Bogdalek said she told two sergeants and a lieutenant about the lie and they told her to say nothing.

“This epitomizes the code of silence we’ve been talking about for the last few months since the Laquan McDonald shooting,” says Andy Shaw, head of the Better Government Association.

Even though an assistant recommended indicting Bogdalek for perjury, State’s Attorney Anita Alvarez decided not to prosecute the case, another example, said the BGA’s Andrew Schroedter, of her “uneven record” when it comes to prosecuting police officers.

In response to a Freedom of Information request, the state’s attorney’s office said since Alvarez was elected she has prosecuted 36 Chicago police officers for crimes or misconduct and 60 suburban, state or county police officers — more law enforcement officers that any previous state’s attorney. They say the statistics show she is not soft on cops as some suggest.

Critics like Kosoglad disagree.

“I blame one person, one group, one office for the proliferation of police lying in this city, and that’s the state’s attorney’s office of Cook County,” he says.

Alvarez’s top aides said it would be “difficult, if not impossible” to prosecute Bogdalek for perjury without cooperation from her partner. “It seems pretty unjust that we would hold Bogdalek criminally accountable” when she came forward, and “others walked away.”

Bogdalek did not return calls seeking comment. She has been stripped of her police powers and is now on desk duty, pending the outcome of a police internal affairs investigation that has taken three years.