CHICAGO (AP) — The Cook County state's attorney says she will dismiss charges against a man who has been incarcerated since 1997 for robbery and murder.

Cook County State's Attorney Anita Alvarez plans a news conference Thursday to announce charges against 37-year-old Alprentiss Nash will be dismissed. Nash was sentenced to 80 years in prison on the charges in connection with the death of a Chicago man on the city's South Side.

Alvarez's office says Nash's case is the first murder conviction to be overturned since prosecutors created a Conviction Integrity Unit in February. The unit is meant to review questionable prosecutions. More than a dozen convictions have been overturned amid allegations of police wrongdoing since Alvarez was elected in 2008.