The Locard Principle of Exchange

I read a lot. Everything from fictional mysteries to nonfiction psychology books. In the course of all this reading, I frequently come across something that might also be seen as applying to poker, even though the concept occurs in a totally different context. This is the first in a series of columns that will illustrate how something from another area might be applied to poker.

In forensic science, there is a ‘law’ called Locard’s Principle of Exchange. Basically, it states that whenever there is a crime, the perpetrator brings something with him that is left at the crime scene and takes something from the crime scene. The goal of forensic science is to find something he left. This may lead to capturing the perpetrator. When you have a suspect, try to find whatever he has taken. That will prove he was there. The evidence may be a huge bag of cash or it may be a few microscopic thread fibers.

What does that have to do with poker? Every time a player plays a hand, he leaves clues. The art of reading your opponents is to find and decipher the clues. It is your job at the table to watch and listen to everything. Then, try to correlate anything you have learned with the actual hand that player held. Here’s an example of this type of detective work: On the flop, a player checks by tapping his knuckles on the table, then later folds his hand. On another flop, the same player checks by tapping two fingers on the table very softly. Another player bets, and he raises. Perhaps his behavior was random, but more likely, he has left you some clues: knuckle check = weakness, finger tap = strength.

While it is almost certain that The Locard Principle is in effect, the unfortunate fact is that for both detectives trying to solve a crime and poker players attempting to figure out their opponent’s hand, one seldom has sufficient resources to examine every potential clue. Imagine that you are in an eight-handed game. You are continually looking for clues. They may be vocal, physical, temporal or of some other variety for each of the eight. Vocal clues come from what they say or how they say it. Physical clues come from their mannerisms, posture, etc. (The checking behavior mentioned above was a physical clue.) Temporal clues arise from the speed with which your opponent takes action. It is impossible to pick up every potential clue, analyze its relevance, and act upon it.

Just as with forensic science, some clues are huge and easy to spot, while some are barely noticeable. The players with great ‘table presence’ or card reading skills notice these microscopic clues. They may observe them consciously or unconsciously, but they definitely pick them up. The lesson here is to remember your opponents are leaving evidence for you to find. You must find it and learn to interpret it.

The huge variety of potential clues makes it difficult for a writer or teacher to explain to an improving player what he should focus on. It is clear that you should focus on your opponents and their behavior, not on your cards, the flop, or the cute waitress (Please don’t tell me you’d rather pick up the waitress than a clue that tells you your opponent is bluffing).

I will end this column, with a description of something that recently happened in the $10-$20 no-limit hold’em game at Bellagio. One of the players was somewhat drunk. He steadily continued to consume glass after glass of wine. He was playing a very loose, aggressive game, and applying a lot pressure with frequent raises and reraises. He was, however, slurring his words a little and knocking over his chip stacks, which were often poorly sorted. When he bet or raised, he’d take a somewhat random handful of chips and toss them into the pot. An early position player raised to $80, another player called, I called with a marginal hand (this is poker code for a hand I shouldn’t have played), hoping the drunk would call behind me. Instead of calling or making one of his usual sloppy raises, he meticulously counted out $380. He carefully pushed his neatly-stacked raise into the pot. The initial raiser and the drunk ended up getting all-in preflop. The drunk had kings, which held up against his opponent’s jacks. The drunk dragged a huge pot and was once more sloppily stacking his chips. No similar situations occurred, but I’m certain that the sight of his kings sobered him up enough to realize he didn’t want to make a mistake or commit an impropriety, and this caused his suddenly-careful behavior. A few hands later, he made another sloppy raise. I wasn’t involved, but I would have bet a lot that he didn’t have aces or kings. He left with some equally drunk friends a little while later.

The lesson to learn is to keep looking for the evidence of what your opponents have, and sometimes you’ll find it. And some of those times, you’ll get an opportunity to use it. ♠

Steve ‘Zee’ Zolotow, aka The Bald Eagle, is a successful gamesplayer. He has been a full-time gambler for over 35 years. With two WSOP bracelets and few million in tournament cashes, he is easing into retirement. He currently devotes most of his time to poker. He can be found at some major tournaments and playing in cash games in Vegas. When escaping from poker, he hangs out in his bars on Avenue A in New York City -The Library near Houston and Doc Holliday’s on 9th St. are his favorites.