Forensics

Paper instructions:
Comment and respond to both in a substantive way; a minimum 300 words for each. I need in text citations and also your references for where you got the information. Ask questions so someone will be able to respond.

1. Recovering Fingerprints from a Crime Scene

Fingerprints at crime scenes come in three forms: visible, impression and latent. Visible prints are visible to the human eye without any enhancement. Visible fingerprints are normally made by the finger coming in contact with another material, such as blood, dirt, grease, and oil. Impression prints are a three-dimensional fingerprint indentation in a soft surface, such as tar, margarine, or putty. Latent prints are developed based on the secretion of oily sweat from friction ridge skin, which leaves an impression of the fingerprint when the finger comes in contact with a surface (Gaensslen, Harris, and Lee, 2008, pp.132-133).

Latent prints are developed utilizing three methods: physical, chemical, and combination or special illumination. Physical methods involve the application of fine particles to the fingerprint residue, utilizing a brush to apply the particles to the surface area. The particles collect on the residue. Tape is then used to lift the fingerprint. The fine particles adhere to the tape, forming an impression of the fingerprint. The tape is then placed onto a card of contrasting color. Powder dusting can be used on nonporous surfaces. Another type of powder testing is the magnetic brush technique. Magnetic powder is used in place of the traditional powder. The standard brush is replaced by a brush that contains a small retractable magnet. The magnetic brush technique is effective on a wider variety of surfaces than traditional powder dusting. The final physical method is small particle reagent (SPR). A fine powder solution is sprayed or dipped, causing the particles to adhere to the residue. SPR is commonly used on wet evidence items (pp.134-135).

Chemical methods include: iodine fuming, ninhydrin, super glue, and physical developer. Iodine fuming involves the turning solid iodine into iodine vapor. The vapor is deposited onto the ridge patterns of a latent print impression on porous surfaces. Ninhydrin is a chemical which reacts to amino acids contained in fingerprint residue, forming another compound called Ruhemann’s purple, when sprayed, printed or dripped. Ninhydrin is normally used on porous surfaces. The fingerprint pattern is further enhances through the use of other chemicals and alternate light sources. Super-glue vapors interact with latent print residue to produce a solid matrix polymer on the ridges. The polymer is further enhanced utilizing chemicals which produce dye stains. The prints can be further enhanced through the use of alternate light sources or laser illumination. Physical developer is a photographic process in which metallic silver is produced on a latent print image through a chemical reaction. This process is most commonly used for latent prints on paper, nonabsorbent surfaces, and pressure sensitive tapes (pp. 135-137).

High intensity alternate light sources and lasers can be used to locate and visualize a latent fingerprint by illuminating the print from an oblique angle (pp. 137-138).

Powder dusting is the most common method for collecting fingerprints at a crime scene on items that cannot be removed from the scene. When possible, evidence that may contain fingerprints should be removed from the crime scene to be processed in a crime lab (Hanson, 2006).

James A. Bailey (2003) conducted research on the differences in effectiveness between nonmagnetic fingerprint powders and magnetic fingerprint powders on ceramic surfaces. The study determined that even though magnetic powders cause more background discoloration than nonmagnetic powders, magnetic powders produce superior quality latent prints. Magnetic powders produced adequate ridge detail on 35% of the test objects and excellent ridge detail on 15%, while nonmagnetic powders produced good ridge detail on 30% and none of the samples were rated as excellent.

The Federal Bureau of Investigation has been involved in research to obtain latent fingerprints from dead bodies since the 1970s. Decomposition, harsh environmental conditions, perspiration, and the shedding of skin cells, complicates the ability to obtain usable fingerprints from dead bodies. The FBI research determined that the utilization of glue fuming techniques at the scene, following an initial examination by a medical examiner, followed by the application of magnetic fingerprint powders at the morgue during autopsy, provided the best opportunity to obtain identifiable prints from the body Futrell, 1996).

How do you collect, handle and analyze the left half of a torn check recovered as evidence at a crime scene?

Document evidence must be handled and packaged with care in order to protect any fingerprints, trace evidence, hairs, fibers, or other particles, that may be present on the document. Document evidence should be placed inside a sheet protector immediately in order to preserve trace and fingerprint evidence. The investigator, questioned document examiner, and forensic scientist should coordinate their efforts in order to determine what evidence should be processed first, and the type of examinations to be performed. Some forms of chemical latent print examinations can cause ink to run, which inhibits the ability of the questioned document examiner to perform his or her analysis (Gaensslen, Harris, and Lee, 2008, pp.159-161).

Voice Print Evidence

Voice print identification is a combination of both aural (listening) and spectrographic (instrumental) comparison of one or more known voices with an unknown voice for the purpose of identification or elimination. Voice identification is based on the theory that every voice is individually characteristic enough to distinguish it from others through voiceprint analysis. Voice uniqueness is developed by the sizes of vocal cavities and the manner in which the articulators or muscles of speech are manipulated during speech. More than 7,000 voice identification cases have been processed by certified voiceprint examiners since 1967 (Voice Print Identification, n.d.)

A Federal Bureau of Investigation study of 2,000 voice print examinations conducted by the FBI, revealed an error rate of 0.31 percent for false identifications, and 0.53 percent for false eliminations. There is disagreement within the scientific community on the degree of accuracy of examiners under all conditions, there is agreement that voices can be identified (Koenig, 1986, as cited in Cain, Smrkovski, and Wilson).

Once a suspect has been developed, investigators obtain voice samples by consent, or through a court order. Court orders should clearly articulate the minimum number of samples to be obtained, the manner of speech and the method to be employed. Speech samples should contain exactly the same words and phrases as those in the questioned sample. There is no universal standard for the number of words required for identification. Recorded evidence should be wrapped in tinfoil in order to prevent contamination from a magnetic field. Analysts should not review investigative reports in order to prevent allegations of bias. Aural and spectrographic examinations are conducted by the analyst in a laboratory setting (Cain, Smrkovski, and Wilson).

There are 30 known trials in the federal court system in which the question of aural-spectrographic voice evidence was addressed. Evidence was admitted in all but three cases. On appeal, the Second, Fourth, and Sixth Circuits held the evidence admissible. The District of Columbia did not. The United States Supreme Court has refused to review and decide on three cases brought before it. Several state courts have admitted the evidence (Cain, Smrkovski, and Wilson).
References

Bailey, J. A. (2003, Mar/Arp). An Evaluation of Magnetic and Nonmagnetic Fingerprint Powders on Ceramic Materials. Journal of Forensic Identification, 53(2), retrieved from ProQuest, November 17, 2013, 162-168.

Cain, S., Smrkovski, L., & Wilson, M. (n.d.). Voiceprint Identification. Retrieved from ExpertPages.com: http://expertpages.com/news/voiceprint_identification.htm

Futrell, I. R. (1996, April). Hidden Evidence: Latent Prints on Human Skin. FBI Law Enforcement Bulletin. 65(4), retrieved from ProQuest, November 17, 2013), 21-24.

Gaensslen, R., Harris, H. A., & Lee, H. (2008). Introduction to Forensic Science and Criminalistics. New York, NY: McGraw-Hill.

Hanson, D. (2006, July). Improved Fingerprint Acquisition. Law and Order, 54(7), retrieved from ProQuest, November 17, 2013, 104.

Koenig, B. (1986). Spectrographic Voice Identification:a forensic survey.Journal of Acoustical Society of America, 79, 2088-2090.

Voice Print Identification. (n.d.). Retrieved from Forensic Tape Analysis Inc.: http://www.forensictapeanalysisinc.com/task%20description/voice.htm
2. Any investigator entering this type of scene should be properly clothed to prevent contamination. At the very least latex gloves must be worn. Prior to entering the bedroom, the bedroom should be thoroughly documented to include photographs, video along with a rough sketch of the layout. The investigator should identify obvious pieces of evidence and note their location. If entering and maneuvering inside the room would damage or alter those pieces of evidence same should documented and/or collected and secured. An example of this would be blood spatter evidence.

A brief evaluation of the victim should be conducted in conjunction with the medical examiner. The purpose of this evaluation as it relates to fingerprint evidence would be to identify signs of trauma or the mechanism of injury. Any obvious signs of trauma on the victim may clue investigators in on an item or object that was utilized to inflict the trauma. The investigators can then attempt to locate that object inside the residence.

After examining the body, a systematic search of the room should be conducted to identify any potential fingerprints. Visible prints, or prints that do not need “enhancement” or “development” would most likely be the first prints to be discovered (Gaensslen, Harris, and Lee, 2008, p.132). These prints would be visible to the naked eye on a variety of surfaces in the room. Latent prints, or a print that “requires additional processing to be rendered visible”, would be located next.

The next step would be to recover the prints. Due to the fact that latent prints are hidden, locating and identifying them represents more of a challenge to an investigator as compared to visible prints. First, a search for latent prints should be conducted in logical areas that a suspect may have come into contact with. Windows, doors, and other surfaces such as table tops are the most common. Depending on the specifics of the crime scene other areas may become relevant such as a jewelry box or picture frames. Recovery of latent prints can be done utilizing several different methods. One manner is to secure and collect items that a suspect may have handled. The items are properly packaged and submitted to a lab. If this method is chosen, special attention must be paid to ensure proper packaging of the item so that the print is not lost. Items containing prints can be classified in two categories, porous and non-porous. Porous objects include paper, wood and cardboard. Non-porous items include firearms, glass and shell casings. The Buruea of Alcohol, Tobacco, Firearms and Explosives recommends that non-porous objects be packaged in a manner that prevents that item from coming into physical contact with the container. For instance, a firearm should be placed in a cardboard container and secured with wire ties or plastic cable ties to prevent to loss of a print due to shifting. Porous objects can be packaged in envelopes or plastic evidence bags as the latent residue has been absorbed into the object and will not be lost due to shifting.

In addition to collecting items and then submitting them to the lab for analysis, Gaensslen, Harris, and Lee (2008) discuss other methods for recovering latent prints at the scene including physical methods and illumination. Physical methods involve the use of dusting powders. The dusting powder is spread across a surface such as a table top where the particles in the dust will adhere to the latent print residue. Once a latent print is revealed via dusting it should be photographed. After it is photographed, clear tape is then placed over the print, the tape is removed and secured to card.

The illumination method involves the use of an alternate light source. As Gaensslen, Harris, and Lee (2008) note, “sometimes latent prints show up better under illumination by certain wavelengths of light (Gaensslen, Harris, and Lee, 2008, p.138). An alternate light source may identify a surface that contains a latent print that is not clearly visible and it also may allow for a room to be processed more efficiently than dusting. Once a latent print is identified via ALS, the print can be dusted and lifted or the item that the print is on can be collected and packaged for submission to the lab.

First, the half-torn check should be photographed and documented. The investigator collecting the item should be wearing latex gloves. The item should be picked up using either forceps or tweezers. Once the item is collected it should be protected in a protective envelope or sheet protector. This allows the document to be preserved along with any potential fingerprints that may be on it. The item should not be folded or written on and handling should be minimal.

Analysis of the half-torn check could include comparison of torn edges from another check to find a physical match. Other characteristics such as watermarks, fibers and dyes can be compared. Ink comparisons between any writing on the check and recovered pens can also be conducted. Mechanical impressions from items such as rubber stamps can be compared to the items that were used to create the impression. The check can also be examined for indented impressions created by writing from the previous check that was communicated to the recovered item. Lastly, the check can be examined for the presence of any latent fingerprints.

http://soundevidence.com/

Sound evidence is the website for Dr. George Papcun. He specializes in the forensic analysis of the sounds of speech. Specifically, Dr. Papcun’s expertise includes “analysis of recordings, enhancing the intelligibility of recordings, determining whether recordings have been altered, speaker identification, memory for voices, voice lineups, using voice to determine speaker veracity and voice morphing” (Soundevidence.com.2013).

This website provides an overview the science of voice-printing including the physical properties that are used to classify individual characteristics of a voice. Dr. Papcun is a subject matter expert that has testified is some high profile court cases including one involving Rodney King and most recently the George Zimmerman trial in Florida.