Brittney Griner released: How do prisoner swaps work?

Brittney Griner has been released from detention in Russia as part of a prisoner swap deal between Moscow and the United States.

The basketball star is safe and on her way home, while notorious Russian arms dealer Viktor Bout, held in American prison for 12 years, has also been freed as part of the exchange.

Dr Richard Stoll, a university professor from Houston, Texas, who specialises in international relations, explains how prisoner swaps can work between countries following the news.