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Fragile (Sensitive) Fingerprint Recovery from Mylar Surfaces


Michael Byrd
Crime Scene Investigator
Metro-Dade (Florida) Police Department

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Recently an investigator with our unit was dispatched to a clandestine drug lab, (referred to on the streets as "grow house"), which was working out of a residence in a local neighborhood. The residence was a typical home in a middle class neighborhood. The interior of the house had been transformed into a cannabis-hemp greenhouse. The house was void of any furniture as the rooms were transformed into a green house for the sole purpose of the cultivation of marijuana. Inside furnishings were lights, plants and irrigation equipment.

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The entire wall space of each room was covered with a mirrored mylar window tint — typically used in automobiles. The reflective tint was probably in place to assist the lighting system in the growing process and also cut down on the moisture from absorbing into the drywall. The mylar sheets were mounted to the walls with a thick adhesive tape. Using a flashlight at a 10-25 degree angle (oblique lighting technique) the investigator could see very defined ridge detail throughout the surface of the mylar. While attempting to use a conventional mechanical method of recovering (brush and powder or magnetic powder and applicator) the impressions, the mechanical process created friction, which removed the ridge detail from the surface of the mylar. Attempts to remove the large sections or sheets of mylar resulted in an immediate rolling and crinkle of the sheets due to static. A small section of the mylar containing a defined ridge pattern was removed from the wall. The impression was developed mechanically, but during the process of using the transfer - lifting medium, (tape) the ridges again were removed. Again, the sensitivity and the force of rubbing the lifting medium created enough friction which literally rub out the ridge detail.


Using common sense, and through knowledge gained from the experiences, the investigator used a permanent marker (Sharpie marking pen) to mark the sections of the mylar where defined ridge patterns were present. He then carefully cut out the sections of Mylar film and gently placed them in shirt (clothing) boxes for transportation. A number of methods were suggested for the recovery of the ridge patterns or prints. One of the methods suggested was using the superglue fuming technique. The general purpose of using superglue as a tool in the field is to fix the print so it is less destructible during transportation. Since the print had survived transportation, it was still an option for development. After reviewing our options, we chose to use a static-tap-and pull method that Agnes Sirisky, a co-worker, and I had come across several years back when working with sensitive prints deposited on dusty surfaces. The procedure is simple, yet requires extreme patience and practice to be successful.

Magna powder was gently applied to the surface of the mylar. The excess powder and debris was blown from the surface using a small can of compressed air. Static is removed from the lifting medium by taking each end of the lifter (tape) in your fingers using both hands, and working the tape back and forth in a half circular motion. Once the static is removed, and while still in a half circle position, the center of the tape circle is placed over the center of the developed print and the tape is just allowed to freely drop over the print. The tape is then tapped several times over the print area. The lifter, (tape), has elasticity and traits similar to human skin and the tapping allows for bounce and rebound into the matte texture or fragile print as opposed to being tightened and stretched smoothly over the surface. Lightly run your finger over the tape and then lift the tape gently from the surface and place it on your lifting medium.

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During a class which I attended as a student in modern fingerprint technology other uses were found for this technique. Criminalist Bridget Lewis of the Iowa Division of Criminal Investigations and I were paired as partners in the class. We worked on various techniques and were able to successfully lift prints from different matte finished surfaces including human skin, where the process retrieved the print with minimal background from the surface.

Conclusion: This technique again proved to be a successful tool in recovering ridge detail from a fragile surface. Extreme patience and practice is needed during the process for success. It is an added tool and may not work on everything. You won't know until you practice and have success with the process.


About the Author

Mike Byrd (1955-2005) joined the Miami-Dade County Police Department in 1983 and started with the Crime Scene Investigations Bureau in 1987. He took an exceptionally active part in the science of forensic crime scene investigations, including development of new techniques, publishing methodology of crime scene procedures, and teaching. Mike developed new techniques for gathering and cataloging crime scene evidence including the lifting of fingerprints, vehicle tire impressions, and footwear impressions.

Mike's methods and analysis withstood the scrutiny of the criminal justice process. He published more than thirty crime scene articles on crime scene evidence collection and for the International Association for Identification and was awarded The Good of the Association Award in 2002 for his innovative identification methodology and techniques. He taught crime scene investigation procedures and techniques at police departments around the country and took great pride at instructing smaller Florida police departments in the latest techniques in evidence gathering.

Mike performed the tough detailed oriented forensic work at many major crime scenes and disasters over two-decades. He gathered, processed, and identified the DNA evidence used to convict the Tamiami Strangler for a string of heinous murders in 1994. His thoughtful gathering of evidence at the Valujet crash allowed families to reach closure for the deaths of loved ones.

Mike Byrd died after a more than two year battle with multiple myeloma cancer. Annually, the Police Officer Assistance Trust awards the Mike Byrd Crime Scene Investigation Scholarship in his honor.

Articles by Mike Byrd


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