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A good crime scene investigator collects evidence with the goal of solving the crime, and holding the person who committed the crime accountable. It doesn’t matter how great a fingerprint or shoe print is if it never gets admitted in court.

During the year, Lt. Owen McDonnell of the Caddo Parish Sheriff’s Office, in Louisiana, and I show crime scene investigators a variety of ways to develop and lift impression evidence. Here, we discuss admissibility of impression evidence and best practices to make sure the evidence you find at the crime scene makes it to the courtroom.

Dick Warrington: Owen, let’s begin by reviewing the types of impression evidence that are admissible in court, so we can then learn how
to collect the evidence.

Owen McDonnell: Impression evidence is any evidence that leaves behind a distinctive pattern when contact occurs, which can then be developed or captured for subsequent comparison to indicate the source of origin. The evidence can include footwear, latent prints, tool marks, bullet striations, bite marks, gouge marks in traffic investigations and others. The reliability of the source of origin determination is contingent on the quality of the impression and varies based on the specific discipline.

DW: What makes evidence admissible in court?

OM: The recovery of the evidence remains separate from testifying as to the originating source determination. Crime scene investigators (CSI) are primarily responsible for recovery of the evidence. Expert witnesses are responsible for providing testimony as to source
attribution. The court must determine if the witness is qualified to testify regarding his opinion and if the science behind the determination is sound. Going into that area involves Federal Rules of Evidence Rule 702 and the Daubert hearing process.

DW: So, we’re talking about admissibility of the evidence versus admissibility of the conclusion. 

OM: Yes, but for the purpose of this article, let’s stick to making sure the evidence itself is admissible. Let others fi ght about the expert testimony.

DW: Right. So, what types of problems can arise over admissibility of the evidence?

OM: The greatest problems arise over traceability of the evidence back to its location of recovery. How can we prove the impression evidence presented was recovered from the source the crime scene investigator claims? More impression evidence is suppressed due to incomplete documentation rather than problems with recovery techniques.

DW: How can problems with admissibility be avoided?

OM: Through the use of proper on-scene documentation like notes, photographs, or diagrams, and complete chain of custody.

DW: Let’s go into that a little more. How can CSIs ensure the traceability of impression evidence to the scene?

OM: Prior to any development, the area with the impression should be photographed using overall, mid-range and macro photographs. Mid-range photographs are critical to establishing relationships of evidence within the scene. After the original scene documentation photographs are taken, place markers or sticky notes next to the impression area to demonstrate to the jury the exact location within the scene. 

Take additional photographs after any enhancement techniques showing the impression in situ. Measure and record the location both in notes and reports. Also document the techniques used to recover the evidence. The chain of custody becomes critical and should be written documenting each and every transfer, no matter how brief.

DW: How do you present evidence in court?

OM: This depends on the type of evidence. The original evidence, if available, is always the best evidence. That said, photographic enlargements and photographic documentation of the location should also be part of your presentation. Electronic enlargements are of great use in educating jurors as to the interrelationships of items within the scene.

DW: What presentations are most effective in court?

OM: This again depends on the evidence. There is much to be said for the jury being able to touch and hold the original evidence, as well as competent testimony regarding the evidence discovery, documentation and collection. Increasingly, we are seeing electronic presentations, such as PowerPoint, being used to project images onto screens as visual aids. With high resolution cameras and photo capture of microscopy, we can show the jury our observations in much greater detail than ever before. 

This is of tremendous value as the old adage of a picture being worth a thousand words stands the test of time. You can tell a jury, but allowing them to see what you saw helps them to believe it much better than mere words.

DW: What are some potential problems to be aware of when presenting evidence in court?

OM: Don’t overstate the value of the evidence or your skills. If you omitted a step, admit it. Don’t try to cover it up. We are humans, and sometimes we make mistakes. Another tip is to check to see how an electronic presentation will look on the same or similar equipment prior to court. If you create a presentation and the image is blurry or too low a resolution to clearly present when enlarged, avoid it. In some instances, no image is better than a bad image. Trying to convince the jury you can see something when they are looking at the same image and they cannot see it, only causes them to doubt you. And if they don’t believe you about this, it may affect the credibility of your entire testimony. They may wonder, if he or she tried to fool me on that, what else is he or she not telling me?

DW: Any other tips, suggestions, etc. that we haven’t covered?

OM: CSIs have great training and are meticulous in their documentation and collection skills. We perfectly package and document each and every piece of evidence we plan to turn in. Yet, we sometimes forget to bring that same attention to detail to the evidence that stays in our labs. While we have great memories, let’s not rely on them too much. For example, CSIs often lift a stack of prints at the scene but occasionally wait until they return to the office to finish filling out the latent cards. But, what if you mislabel a print as coming from the inside of the window on a burglary when in reality it was from the outside? While it may still be the burglar’s print, the probative value is tremendously different. One proves presence outside the window, the other proves at least their hand was inside the building. 

Finally, take time to learn how to use your equipment and practice your collection techniques. The scene is never the best place to use a technique for the fi rst time. Seek the help of others. The mark of knowing what you are doing is knowing when you need help. 

Owen McDonnell is Lieutenant / supervisor of the Caddo Sheriff’s Office Crime Scene Investigations Division in Shreveport, LA. He provides training in crime scene, fingerprint development and comparison techniques, and workshops through IAI. He holds IAI certifications as a Senior Crime Scene Analyst, Ten Print Fingerprint Examiner and Latent Print Examiner. Lt. McDonnell holds a Master of Forensic Science Administration Degree from Oklahoma State University Center for Health Sciences.

Dick Warrington is in research and development, and also a crime scene consultant and training instructor for the Lynn Peavey Company. dwarrington@peaveycorp.com.

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