The report that all espionage charges against Temple University physicist Xiaoxing Xi have been withdrawn raises the obvious question: How could things have gone so wrong? According to published accounts, prosecutors and agents saw documents that appeared to be suspicious and concluded – erroneously – that they were schematics for a particular device. Reading the story raises a concern about cognitive biases at work. The term biases does not refer to a prejudice or dislike, but rather a process in which the brain biases the observer to favor a particular conclusion. One particular type, “confirmation bias,” is common and particularly human: What a person expects to see colors the perception of what is then examined. Confirmation bias is no stranger to criminal and forensic investigations. It played a part in the misidentification of a suspect in a 2004 terrorist train bombing in Madrid, and its effect has been shown repeatedly in research. Whether it is a DNA analyst or a fingerprint examiner, erroneous information or our expectations can cause the person to see what is …