Contribución del área del desempeño profesional a los objetivos del banco

When foreign debris on one item corresponds with the component material of a poten- tial source item, it is not always clear whether the correspondence is due to direct con- tact, contact with an alternative source, or secondary transfer from the original source. Materials are often transferred through an intermediary source that was the recipient of the original transfer (Suzanski, 1989; Lowrie and Jackson, 1994; Grieve and Biermann, 1997; Taupin, 1996). When fibers like the component fibers of a garment or other fabric source are found on a garment from another person, direct contact is supported when most

Figure 8.13 White spheres (CaCO2) and hollow black and brown spheres in sieved ashes from

T-shirt burn.

types of noncomponent debris on the first garment are also found on the second garment and few types of debris fail to correspond (Cwiklik, 1999). This degree of correspondence is usually observed only when the garments are minimally changed from the immediate post-contact condition. That is, the garments of neither individual were worn very long after the incident under investigation. This condition was met in Case Examples 8.1, 8.9, and 8.10.

In most cases, the garments of at least one of the individuals suspected of being in contact continue to be used after the contact incident, allowing transferred debris to be lost and additional debris to be deposited. It may then be possible to establish an associa- tion that includes a wider range of possibilities including both direct contact and contact through an intermediary source. Sometimes an association other than direct contact can be highly significant, and in other cases, a finding of indirect rather than direct contact may be exculpatory. This is discussed in Case Examples 8.11 and 8.9, respectively. The degree of correspondence of non-component debris influences the strength of an associa- tion, even if direct contact cannot be established.

Sometimes it is of interest to determine whether a garment was worn inside out, or in what sequence the layers of several garments were worn by an individual. The expectation is that surfaces that were in direct contact exhibit a higher number of component fibers from the adjacent garment and a close correspondence of non-component debris, whereas debris from the other surfaces exhibits a lower degree of correspondence. This must be evaluated with respect to the capacity for persistence and retention of each recipient fabric.

Finding potential sources for predominant non-component debris increases the strength of an association. When transfer through an intermediary source cannot be elim- inated, the examiner should obtain reference samples of debris from logical intermediary sources. If direct contact with an intermediary source is indicated, direct contact with the

Traces and Debris 173

source initially suspected of being in contact can be eliminated. Transfer via an interme- diary source is illustrated in Case Example 8.1; the examiner concluded that hairs found on the clothing of a victim and attributable to the spouse of a suspect were deposited by secondary transfer from the suspect’s sweatshirt.

CaSe exaMPLe 8.9

Direct transfer or transfer from an intermediary source?

Several students who shared an apartment in student housing had a birthday party for one of their group. The three students in the apartment next door, a married couple and a single woman, were their friends and were invited. The single woman left early to study for a test and went to bed early as well. She reported being digitally raped by an intruder she saw only by the light of her computer screen saver. She described the intruder as one of four men at the large party. Police collected her bedding and took her to the hospital, where swabs were taken and her clothing (a T-shirt) was collected. Police went to the residence of the man she described, a non-Caucasian student in his senior year and about to graduate. He had walked home alone, with no witnesses, and went to sleep without changing clothes. Police took him to the hospital as well, where medical swabs and clothing were collected. His hands were also swabbed for possible evidence of vaginal secretions. The sexual assault kits, clothing, and bedding were sent to the crime laboratory.

Laboratory test results yielded no foreign DNA from the vaginal or penile swabs, but the hand swabs from the young man yielded DNA from at least four individuals. The victim’s DNA profile was included in the mixture from the hands, but the body fluid origin could not be identified, so it was not known whether the DNA could have been transferred during a handshake. Foreign hairs, including pubic hairs, were found on the bedclothes, but the hairs were of Caucasoid origin and unlike those of the suspect. The victim said that her last sexual intercourse had been six weeks earlier.

The suspect’s clothing exhibited no hairs that could be attributed to the victim, but did exhibit four purple or maroon fibers of the same type, composition, and dye profile as the unusual fibers of the victim’s bedspread comforter. The suspect was arrested, tried, and convicted. When the case was revisited two years later, the possibility of intermedi- ary transfer was raised. No debris samples had been taken from the apartment where the party was held and where the young woman was a frequent visitor. Thus, it could not be established whether or not fibers from the comforter were a part of the debris in that household, especially on the furniture in the living room where the party was held. Nor were the clothing or bedding available for reexamination; they had been destroyed because of a clerical error. Neither the young woman’s T-shirt nor the young man’s cloth- ing had been sampled for debris — only for target fibers.

Could a comparison of samples of debris from the clothing have indicated contact between the suspect and the victim or her bedding? Or would transfer of the purple fibers via intermediary contact be suggested, which could be exculpatory? A target search did not permit the case questions to be adequately addressed, and when the issue was revisited, it was too late.