Comparative Sciences

Latent Prints Overview

This section processes and analyzes various items of evidence in an attempt to identify or exclude who may have touched an item or surface. Several different chemical processing methods are used at Miami Valley Regional Crime Lab (MVRCL) to recover latent (invisible to the naked eye) finger, palm, and - on occasion - bare footprints from items of evidence. Examiners also examine lifts that have been taken at the scene and submitted by investigating agencies. When latent prints of value are recovered, they can be compared with the known prints of the person or persons associated with the crime. The Latent Print Section maintains an Automated Fingerprint Identification System (AFIS), which includes a digitized database of known fingerprints and palmprints. These known prints can be used for direct comparisons, or latent fingerprints and palmprints from a crime scene can be entered and searched against the database. This can provide potential new suspects if identifications are made as the result of an AFIS search. MVRCL's AFIS also provides the capability to remotely search available Ohio BCI and FBI databases.

Latent prints can be left on porous, non-porous, or semi-porous surfaces that have been touched with bare skin. Non-porous items that are smooth, flat, and clean, like glass, plastic, or metal, are generally good surfaces for latent print recovery. Porous items such as paper, cardboard boxes, and receipts are also suitable for processing. Semi-porous surfaces include Styrofoam and shiny coated cardboard or heavy papers. If there are ever questions about an item's suitability or the best method for latent print processing or recovery, the Latent Print Section is available to answer questions or provide recommendations.

Standard Operating Procedures

  1. Evidence Handling and Case Assignment
  2. Automated Fingerprint Identification System
  3. ACE-V Methodology and Case Documentation
  4. Evidence Processing
  5. Processing Methods
  6. Report Writing
  7. Quality Assurance

For additional help, view the Appendix A - Definitions and Abbreviations

Firearms Overview

This section performs analyses in several areas of comparison. The examiners can identify the firearms used during a crime by microscopically comparing crime scene bullets with known test-fired bullets.

Serial numbers which have been damaged can be restored using chemicals. Thus stolen firearms can be traced to their owners.

This section also maintains an open case file that contains cartridge casings from unsolved homicides and serious felonious assaults for comparison with weapons submitted by police agencies.

Standard Operating Procedures

  1. Barrel and Overall Length of Firearms
  2. Caliber, Shot, Wad Determination
  3. Comparisons
  4. Distance Determination
  5. Measurement Uncertainty
  6. Evidence Handling
  7. Administrative Manual
  8. Quality Manual
  9. NIBIN
  10. Safe Firearm Handling
  11. Serial Number Restoration
  12. Test Firing
  1. Jennifer Yoak

    Technical Leader