Why are ex-convicts in the US barred from voting?

Hasan Zarif was unable to vote for more than three decades.

For 16 of those years he was a convicted criminal serving a life sentence in a US prison for first degree murder.

Zarif was released for good behaviour in 1989 but Virginia - along with two other US states - automatically removes felons' right to vote even after they are out of prison and no longer on parole.

In 2007, then Virginia Governor Tim Kaine renewed Zarif's civil rights - allowing him to vote and also to stand for public office - in recognition of his efforts as an ordained minister in helping rehabilitate others.

The Sentencing Project estimates that one in 40 Americans is disenfranchised because of a felony conviction. That rate for African Americans is one in 13.

Zarif spoke to the BBC about why voting is so important and how it can help criminals who struggle to become useful members of society again.