Lawsuits against the police or other government entity are both legally and factually complex. The likelihood of success can change radically based on as little as a single small fact. They are rarely successful because police departments, officers and municipalities have a wide range of immunities they can assert that prevent any recovery. Additionally, the law also provides the police considerable leeway in executing their duties. If you can prove the defendants are not immune and were liable under the law, you still must prove the acts of the police caused an injury recognized for recovery.
If you believe you have a claim against a police department, law enforcement officer, or other law enforcement agency you should talk to an attorney to assess the facts of your claim and determine the best strategy in your situation.