Astrid Proll was the younger sister of Thorwald Proll, who participated in the April 1968 bombing of two Frankfurt department stores with Gudrun Ensslin, Andreas Baader, and Horst Söhnlein. Astrid Proll joined Ensslin and Baader soon after they became fugitives from the law in 1970 (her brother Thorwald was soon dumped from the burgeoning gang soon thereafter).

Proll was arrested in May of 1971 but escaped and fled to England. She was found in England in 1977 and extradited. Once back in Germany, charges against her stemming from her original arrest were dropped when it was learned that the state had withheld evidence that would have cleared her.