Tactically Introducing Evidence

BY: Detective Jon Rappa

One of the most frequent questions I get asked during my interrogation classes is when is the right time to introduce evidence to your suspect. While there are no hard and fast rules, I have learned over the years that it is best to take a systematic approach when showing evidence to your suspect rather than merely throwing evidence on the wall to see what sticks.

One of the basic rules of negotiation is to avoid showing all of your incentives at the start of a negotiation. For example, think back to a time you purchased a vehicle from a dealership. You picked out the vehicle you wanted, you took the test drive, and then you sat down with the salesman to discuss the price of the vehicle. The salesman quoted you a price suggesting you were getting a great deal. When you suggested that you were going to check the price at another dealership, the salesman probably asked you to wait for a second, went to the back to speak with his boss, and then miraculously came back with dealer incentives that were not presented to you at the beginning of your negotiation.

Then, as the negotiation continued, and you threatened to walk out again, he was suddenly able to get $1500 on a trade in that he was originally only able to give you $500 for. This back and forth most likely went on for a few hours until you either walk out for good or you got close to the price you wanted.

This is not done by accident. If you walked into the dealership and the salesman put all the cards on the table immediately, there would have been no incentive to keep you at the negotiation table when you decided to look elsewhere. Keeping the same concept in mind, if we enter an interview or interrogation and lay out all of our evidence at the very beginning, we also have nothing to negotiate with when the suspect does not budge.

Introducing evidence normally has the following effects: 1) It gets the suspect to change their position, 2) it can generate conversation, 3) it can shut them down, or 4) it can get them to tell the truth! If we introduce all of our evidence at the start, we limit our chances of negotiating a continued conversation.


Because a suspect may shut down, I never introduce evidence during the interview stage. The interview stage is a non-accusatory fact-gathering stage. During this stage, we are attempting to get a timeline, establish an alibi, and gather facts that could help us build our case. If the suspect shuts down during this phase, we lose any chance at gathering these things. I feel it is best to introduce evidence during the interrogation phase; the phase when we let the suspect know that we know they did the bad thing. If they shut down at this point, you still have a timeline and other possible lies that your investigation could destroy.


This is a great tool to use during an interrogation where the suspect is lying, especially when the evidence is tangible and something they know could exist. For example, let’s assume we are working a case where the suspect is accused of a bank robbery. During the interview stage, the suspect gave you a timeline and said that he was at work, 45 minutes away from the scene of the crime. Because you are an experienced interrogator, you did not call him out on his lie. You allowed him to talk and dig a hole for himself.

During the interrogation, the suspect continued to maintain his position that he was at work. You decide to introduce your first piece of evidence. Cell phone records that show his Geo-Data location; revealing that he was in the area of the bank. You lay it down in front of him; a map of the bank and an icon with his cell phone number. Suddenly panic sets in. He begins to stutter and the rise and fall of his chest become apparent. You lean in, lower your voice, and say, “Brother, you weren’t at work. We both know this. The evidence shows this. Talk to me”.

As he begins to rock back and forth in his chair he replies, “Okay, I wasn’t at work. I was there, by the bank, but I didn’t rob it”. Music to your ears! He changed his position and you are one step closer to the truth! Even if he shuts down after this revelation, you have gotten your suspect to admit he was lying; he admitted that he was in the area. Coupled with other evidence, a good prosecutor can use this later during a trial.


Another thing introducing evidence does is generate conversation. This is extremely important, especially with a quiet suspect. Sometimes we interview suspects who barely speak or they don’t speak at all; they kind of stare at the wall as you go on and on about the facts of the case. The truth can’t be told through silence. Introducing evidence may generate conversation in these scenarios. A conversation may lead to the truth.


Sometimes, when the stars align just right, introducing evidence can elicit the truth almost immediately. Confronting a suspect with hard evidence may be enough to get them to admit their guilt. This is obviously the ideal situation; if only all interrogations were this easy.

The next time you are interviewing a suspect, don’t just arbitrarily throw out evidence against the wall hoping that it sticks. Introduce your evidence when it needs to be introduced. One piece at a time, after the interview and during the interrogation, when you are at a standstill and you need to generate conversation or get them to change their position. Tactically Introducing Evidence can generate fantastic results.