UN Resolution and one BBC Interview

UN Resolution 260, 1948 - On Genocide mentions punishment for criminals who assisted mass killing of civilians in war time.

According to Art. 3. The following acts shall be punishable:

(a) Genocide;
(b) Conspiracy to commit genocide;
(c) Direct and public incitement to commit genocide;
(d) Attempt to commit genocide;
(e) Complicity in genocide.

Art. 7. mentions that those War Criminals cannot be considered as political crimes for the purpose of extradition

Before that Art 2. definition of Genocide includes Killing members of the group or causing serious bodily or mental harm to members of the group;

So Jamaat/Shibir or similar fake-islamic parties who participated in Genocide in 1971 have no other way to escape! Here I attach one relevant interview on BBC News.