You may be able to sue the county (you can also sue the officer).  An employer, including the county, is generally not liable for the criminal acts of its employees unless the criminal act was done in the course of employment, in order to further the employer's goals. Planting evidence to get an arrest or conviction goes to the heart of what the police do--it is part of their job to find evidence, make arrests, and support the prosecutor's office in seeking convictions. Therefore, this criminal act (unlike, say, an officer robbing someone, which has nothing to do with his job as a police officer) is one that since it was committed for and in the course of employment, may be one for which the county is liable. It would be worthwhile for you to consult with an attorney about the situation.