The documentary two-parter exploring American execution interested 4.46m (18.1%) in the 9pm hour, adding an impressive 507,000 on +1.
Meanwhile, Silent Witness maintained a strong 5.78m (23.4%) to lead the 9pm hour, despite losing 300k on last week's opener.
BBC Two's Winterwatch ended with a decent 2.84m (11.6%) in the 8pm slot, while Channel 4's Location, Location, Location held 2.32m (9.4%) as well as 187k on timeshift.
Overall, BBC One topped primetime with 23.5%, ahead of ITV's 18.7% (+1: 1%), Channel 4's 6.2% (+1: 0.8%), BBC Two's 6.1%, and Channel 5's 3.9% (+1: 0.4%).
The Big Bang Theory predictably led the multichannel ratings with 1.47m (5.9%) on E4 and 390k on +1.
BARB ratings data supplied by Attentional