A former San Francisco police lieutenant incriminated in a racist texting scandal has been charged with obstructing the rape investigation of a subordinate officer.

The San Francisco district attorney's office on Wednesday charged Curtis Liu with a felony count of lying to investigators and two misdemeanors charges of obstruction.

In August, a woman reported that then-Officer Jason Lai raped her. Liu is accused of discussing the accusation with Lai before investigators contacted him and then denying he had contact with the suspect.

Prosecutors in March declined to charge Lai with rape, saying there wasn't enough evidence. During the rape investigation, it was discovered that Lai, Liu and two other officers exchanged racists and homophobic text messages.

Liu retired from the department last year. Lai resigned earlier this month.