One of Mac's most difficult situations on the job involves the discovery of Aiden Burn's questionable behavior. Aiden had been sorely tempted to tamper with evidence in order to implicate a rape suspect whose victim decided to press charges against him after he raped her a second time (the victim declined to press charges after the first assault). Though Aiden eventually does not follow through, she had broken the seal on the evidence, and Mac, insistent on preserving the integrity of the lab, felt that his only option was to fire her. Nevertheless, he promises Aiden that he will bring the rapist to justice, a promise that he makes good on (with Aiden's help in a sad irony) in episode 2.23 "Heroes."