Full text
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| Author(s): |
Daniela de Oliveira Francisco
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2021-08-12 |
| Examining board members: |
Cintia Fridman Rave;
Alexandre Torchio Dias;
Alexander Augusto de Lima Jorge
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| Advisor: | Cintia Fridman Rave |
| Abstract | |
Fingerprints are traces commonly found in crime scenes that can be used in forensic analysis to obtain STR profiles from the DNA recovered from them, this technique being known as Touch DNA. Several factors can affect the obtaining and quality of these profiles, such as the type of surface on which the genetic material is deposited. In Brazil, the most recurrent crimes are those committed with bladed weapons, theft of vehicles and cyber crimes, and in many cases the use of DNA profiles in investigations is not used because touch DNA is not considered as a good source of biological material. The objective of this study was to analyze the feasibility of obtaining DNA profiles in different materials for knife handles, knobs and steering wheels for cars, and on computer keyboards through simulated situations of direct transfer. In all, 104 experiments were conducted in order to evaluate the effectiveness of two DNA extraction kits: DNA IQ System and Casework Direct Kit (both Promega Corporation). Nine individuals participated in the study: four men and five women. DNA was collected using the double swab method. The samples were quantified with the Quantifiler Trio kit (Thermo Fisher) and amplified with the PowerPlex® Fusion System (Promega). It was possible to obtain 83 STR profiles (32 extracted with DNA IQ and 51 with Casework), and samples extracted with Casework Direct Kit obtained an average of alleles coinciding with the references samples higher than those with DNA IQ. Of the 83 profiles generated, 31 of them (37.3%) would be useful for identifying the criminal (24 from Casework - 77.4%), considering as the profile utility parameter, the presence of 8 of 13 STR markers from the original CODIS. When considering 8 out of 20 current CODIS markers, 42 profiles (50.6%) would be useful (30 from Casework - 71.4%). Drop-out and drop-in were observed, although in greater numbers for samples extracted with DNA IQ. Variations in the shedder status of the same participants were observed in different experiments, making it difficult to classify as good or bad donors. Experiments with two women were better at identifying the secondary donor than trials with two men, suggesting that women may act more as cell removers than depositors. The Chi-square test showed that the Casework Direct Kit was better for producing useful profiles for an investigation on all tested surfaces (p = 0.001). The Kruskal-Wallis test showed that the type of surface significantly affects DNA recovery for both extraction methods (p = 0.005 for DNA IQ and p = 0.002 for Casework), with the steering wheels obtaining the best results and the knife handles the worst. It is concluded that the Casework Direct Kit was more effective for analyzing touch DNA samples for the three types of materials studied, although other factors, such as the type of surface or environmental quality, interfere in the generation of the profile (AU) | |
| FAPESP's process: | 19/09622-0 - Study of transfer DNA in simulated situations for forensic purposes |
| Grantee: | Daniela de Oliveira Francisco |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |