To be sure, Eric’s diagnosis of psychopathy is not 100 percent. Psychopaths do not tend to be suicidal, or seek fame. They usually come from the ranks of “low socioeconomic status and urban settings,” according to the DSM. Psychopaths must also show certain patterns of behavior as juveniles that include animal abuse. Eric, in all his writings, never mentions that, nor is there any evidence of such behavior. His extreme violence is not a trademark of psychopaths. And Eric does show emotion and feeling: He laments the loss of his childhood friends, he wishes he had more friends at Columbine, and he worries what will happen to his parents after the shootings. (Although Fuselier points out that if Eric really did care about his parents, he wouldn’t have undertaken the shootings.) 
  Their pell-mell behavior makes psychopaths poor employees, yet Eric was a model worker. Lying for the sake of lying, or duper’s delight, is another sign of psychopathy, and Eric told multiple lies. Although he himself also indicates he lies for a specific purpose, or as he says in his diary, “just to keep my own ass out of water.” in other words, Eric needs to lie to stay out of trouble. It doesn’t appear to be for fun. 

- Jeff Kass in the book Columbine: A True Crime Story on why Eric Harris’ post-mortem diagnose of psychopathy is inaccurate.