My friend makes his own peanut butter. How can you know whether or not peanuts are infected with aflatoxin?

Interesting Question. The Aflatoxin/Peanut Butter scare seems to come up every few years -- Here are some interesting googled links with divergent viewpoints -- https://bbrocc.wordpress.com/2010/05/03/aflatoxin-the-peanut-butter-scare-lives-on/ http://realfoodforager.com/why-i-gave-up-peanut-butter/ http://www.foodsafetywatch.org/factsheets/aflatoxins/