Combating the Heroin Epidemic Through Forensic Drug Testing Act of 2017 This bill amends the Omnibus Crime Control and Safe Streets Act of 1968 to authorize the Department of Justice's Bureau of Justice Assistance to award grants to states to address the distribution, sale, and use of heroin, fentanyl, and associated synthetic drugs. Grants may be used to: reimburse forensic science laboratories for efforts to address and prevent testing backlogs; reimburse law enforcement agencies for equipment to identify or detect heroin, fentanyl, and associated synthetic drugs; investigate, arrest, and prosecute distributors or sellers; and support health department services for users.