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Procedure 6101Santa Ana Police Department Santa Ana PD Procedures Manual Copyright Lexipol, LLC 2021/10/01, All Rights Reserved. Published with permission by Santa Ana Police DepartmentTRACE EVIDENCE - 1TRACE EVIDENCE 6101.1 PURPOSE This procedure establishes guidelines for the proper identification and collection of trace evidence. 6101.2 INTRODUCTION Trace evidence is defined as small evidentiary particles and includes, but is not limited to, hair, fibers, glass fragmentation, paint transfers / chips, gun shot residue, fire debris, botanical material, soil, and unknown chemical solids or liquids. Locard’s Exchange Principle states that whenever two objects come into contact a transfer of material will occur. The transfer may be primary (direct) or secondary (indirect) and usually involves trace evidence. Personnel responsible for the collection of trace evidence at any crime scene shall adhere to the following guidelines. Their actions or inactions should be based upon the particulars of each crime scene and firmly rooted in accepted forensic practices. 6101.3 PROCEDURE FOR LOCATING/IDENTIFYING TRACE EVIDENCE The following methods for detecting trace evidence at crime scenes are acceptable. No one method is correct for any given circumstance and it is recommended that more than one, if not all, methods be used to locate potential trace evidence at a scene. 1.Using direct light can be a very effective way of locating trace evidence. The brighter the light source, the more likely the forensic investigator will notice subtle differences in color and contrast of adhering surface particles. 2.Oblique lighting takes advantage of differences in the reflective qualities of particles versus the reflective qualities of the surface on which the particles reside. This method works well under low ambient light conditions. 3.Magnification is always advantageous. This method differentiates between particles with similar gross appearances and for making visible particles, which would otherwise go unnoticed. 4.Use of an Alternate Light Source (ALS) is often useful for visualizing many otherwise invisible evidentiary particles at scenes. It is important to note that different wavelengths used in combination with various filters each may reveal something new and previously unnoticed. The forensic investigator is encouraged to try all combinations of wavelength and filter. 6101.4 DOCUMENTING TRACE EVIDENCE As with any item of evidence, it is imperative that thorough documentation through accurate note taking, sketching, diagramming and/or photography (with and without scale) take place prior to collection. Because trace evidence is small by nature, overall, midrange and close-up photographs depicting where the item is relative to other items in the scene is imperative. Close-up photographs of trace Santa Ana Police Department Santa Ana PD Procedures Manual TRACE EVIDENCE Copyright Lexipol, LLC 2021/10/01, All Rights Reserved. Published with permission by Santa Ana Police DepartmentTRACE EVIDENCE - 2evidence should always fill the frame. Keep in mind that photographic filters may also become necessary to best document the evidence. Notes may include sketches and should be clear, concise and easily read by any viewer. Abbreviations should always be defined. Forensic Notes will become the foundation of your report and are susceptible to both peer review and later discovery. 6101.5 COLLECTING TRACE EVIDENCE In most instances, trace evidence should be collected prior to the collection of biological or fingerprint evidence, although there may be exceptions. Be aware of other forms of potential evidence that could be destroyed or altered because of the collection technique. The following techniques may be applied to the collection of trace evidence: 1.Hand Picking – Disposable or sanitized forceps, tweezers, and magnets, as well as gloved hands, can be used to remove some trace evidence, collecting the larger particles first. Magnification and a bright light sourceaid in this technique. Hand Picking is beneficial because, not only is it a one step process, but also it allows the forensic investigator the ability to document exactly where the particle(s) came from. Individually collected hairs and fibers may be placed on a clean “POST-IT” style paper or weigh paper for later packaging. 2.Tape Lifts - Using manufactured Tape Lifts or a roll of clear “inspected” sealed tape that is by definition free of debris, cut an approximate 20cm strip and apply the adhesive side of the tape to the questioned surface. Be sure not to overload the tape to the point that all adhesive is used. Apply the strip to an inspected clear plastic sheet protector, and repeat until the trace evidence has been sufficiently collected. Be careful with the edges of the tape so as to prevent accidental debris collection. Once complete, the tape roll should be placed back inside the now open heat seal bag for re-inspection. See below for inspection guidelines. (a)Each lift should be sufficiently labeled. Notes should include the name and date of who had previously inspected the tape, where the lift came from, date and time of collection, how the tape lift was labeled, case number, etc. This method is not to be used for wet or oily surfaces. (b)Tape lifting will successfully lift gunpowder particles; however the nitrocellulose in the gunpowder residue will slowly dissolve in the adhesive of the tape. Therefore, the case agent should be advised to contact the Orange County Crime Lab for expeditious processing of the tape. (c)Tape that has not been inspected prior to use shall not be used for trace evidence collection. Inspection consists of viewing the tape roll under the microscope, removing all foreign debris and heat-sealing the tape in a clear plastic bag. The