Sometimes a book finds you at the perfect time. Right now, for me, that book is Criminal Investigative Failures by D. Kim Rossmo, a Canadian criminologist who specializes in geographic profiling. “What we remember depends on what we believe.” That line has batted around my head for days. It helps explain why the retired detective and the victim I interviewed have such different memories of the same exchange that happened 30 years ago. Police reports, with their terse formatting and signatures at the bottom, can mislead readers into believing the content is unadorned, a clean, objective reproduction of an incident. But that’s far from true. They are interpretations, and as such are vulnerable to a vast array of influences: experience and expectation; sleep deprivation and hunger; bias. The victim remembers that after a vicious nighttime attack she was left speechless from shock. The detective’s perception, noted in his report, is that she’s a “cool customer” and “blank-faced.” Mute anguish read as nonchalance.
If pressed, the retired detective would likely stand by his interpretation. Belief perseverance, as Rossmo calls it, is a common pitfall in criminal investigations. “New information becomes assimilated with old information,” he writes of memory, “and the old information has more influence on the new information than vice versa.” First impressions, and the theories that result from them, calcify over time.
Rossmo’s explanation of “cause and effect biases” made me realize how frequently these types of errors occur. He makes the point that people often fail to differentiate internal (psychological) from external (situational) causes of behavior. He gives the example of how the level of force used by a rapist may be contingent on the degree to which a victim resists. I thought of how often people, myself included, attributed the severity of violence in a particular case to personal rage the offender must have had for the victim, or theorized about some triggering event, when in reality the cause may have been situational.
Another Rossmo sentence that resonates: “If you look hard enough, you can usually find some sort of connection.” He quotes a Midwestern detective pursuing a serial rapist for many years as half-joking that he could have convicted three people if it were not for DNA. The wider the field of suspects the greater the chance that at least a few are going to look guilty, either by being at the wrong place at the wrong time, or sharing similar traits or connections as the real offender.
I’m only a quarter of the way through the book but bowled over by what it’s taught me so far. Exclamation points and asterisks run like graffiti down the margins. The error in thinking I most identify with is that we are more influenced by vivid information than abstract data. While researching the Golden State Killer case I’ve heard many stories filled with specific, haunting details --- the pair of penetrating blue eyes staring out from a ski-masked face, the discovered Polaroid of a seemingly-gentle man holding a gun against a woman’s head during sex. The GSK case is a story in search of an ending, and thus new details, vivid but isolated, search for a way to march in line with what we know for sure. Only later do I think about the odds that a home invader would wear a mask and have blue eyes (fairly good, especially for the area in question), and that people hide photos for all sorts of reasons, including depictions of sexual role-playing. Crunch the numbers and show me a graph; I know that’s the more solid evidence. But tell me a story? That’s what I’ll remember.