A Charles City man has been sent to federal prison for failing to register as a sex offender, according to KIMT. 50 year old Charles Gregory will spend 16 months in federal prison. Authorities say he lived in Charles City from May of 2018 until September of 2019 without registering. He was ordered to register as a sex offender for life after multiple convictions of aggravated sexual assault in 1990. Once his prison term ends he will serve three years of supervised release. There is no parole in the federal prison system.