The article spends a lot of time talking about the desire to prosecutor drug-related crimes in San Francisco, and some of the cases that will be dismissed, but has only limited information on the nature of the scandal:
The review of cases comes after police leaders benched [a] veteran narcotics officer ..., whom the department is investigating over accusations that she had an inappropriate relationship with a confidential informant and impeded an active criminal investigation.
The Chronicle first reported Tuesday that San Francisco prosecutors were reviewing at least 132 cases tied to [the officer], and had dismissed 82. Prosecutors have not identified individual cases, so it’s not clear if the 132 under review include any of the 82 pulled out of court.