In Chapter 8 I look at the strategies that people use to gather and interpret evidence, focusing on the classic confirmation bias. I argue that this ‘bias’ covers various different strategies, some of which are reasonable, whereas others are genuine biases. One danger is when investigators misinterpret evidence and these errors cascade undetected through the evaluation process, distorting the evidence presented to the ultimate decision-makers. I argue that, without meta-level insight into the way evidence is gathered and assessed, we risk distorting the impact of that evidence, sometimes with disastrous consequences.