a) Review and Evaluation of Crime Scene Investigation and Evidence Collection:
Evaluation and opinion regarding 1) the actions of the first responder and scene investigators and 2) the evidence documentation, collection, handling, packaging, transport, and storage. This includes review and examination of case file information including police and crime scene reports; crime scene photographs, diagrams, sketches, and videotapes; witness statements; victim/suspect statements; documentation regarding the initial collection, packaging, and preservation of the physical evidence at the scene(s); etc.
b) Review and Evaluation of DNA Laboratory Procedures, Data, Results, Reports, and Conclusions:
Two primary questions that need to be answered when reviewing and examining the DNA laboratory records for a specific case are: Does the data support the conclusions in the final laboratory report and are these conclusions supported by other case information? Therefore, it is necessary to review and examine the DNA laboratory standard operating protocols, the laboratory analyst’s handwritten evidence examination notes, evidence sketches and photographs, serology worksheets (presumptive and confirmatory testing), DNA testing data upon which the final conclusions are based, the DNA data files generated during the analysis using Applied Biosystems software, the source of the population frequencies and evidence of their validity, equipment maintenance records, corrective action records, precautionary measures, final laboratory reports, laboratory accreditation records, communication logs, chain of custody documents, documentation regarding evidence handling, sampling, and storage, etc. Depending on the results of the review, independent testing of remaining evidence samples may or may not be recommended. Unless the DNA analysis is severely flawed, independent testing would unlikely produce different results. However, independent DNA testing might be required in the following instances: a) incorrect interpretation of the DNA data or an inappropriate analysis performed by the laboratory, b) probative evidence items that were never tested, c) when the only evidence is a match with a DNA profile in the CODIS database, and d) additional genetic markers might indicate differences between the evidence and reference samples.
Errors Discovered During the Review of DNA Case Files: The following is a list of errors and mistakes discovered during the review of DNA laboratory records in prior cases: problems with the chain of custody, improper evidence packaging and storage, failure to examine and process probative evidence, misleading and overstating of serology and DNA testing results, lack of controls used in testing procedures, contamination of control and evidence samples, misinterpreting DNA data, disregarding low level DNA in sample profiles, failure to follow laboratory protocols, reporting errors, etc.
Forensic DNA Testing Technology:
DNA stands for Deoxyribonucleic Acid and is the genetic material that stores the inherited traits that are passed on from one generation to the next. The primary type of DNA found in the cells of the body that is tested in forensic laboratories is nuclear DNA. Nuclear DNA is a linear molecule that is packaged in chromosomes within the nucleus of the cell. Humans have 23 pairs of chromosomes – half of the chromosomes are inherited from the mother and half are inherited from the father. Current forensic DNA testing combines PCR (Polymerase Chain Reaction) with STR (Short Tandem Repeat) analysis of those locations in human DNA that differ between people. Approximately 99% of all human DNA is the same. The one percent of DNA that differs between each person contains sequences of repeating nucleotides called Short Tandem Repeats (STRs). STR regions (or markers) are short sequence elements that repeat themselves within the DNA molecule. What is important to forensic biologists is that STR regions are highly polymorphic, which means they are different between people. These repeat sequences are relatively short in length, typically 2-6 bases and the entire STR region is very short (less than 500 bases in length), which means that STRs are less susceptible to degradation and may often be recovered from trace amounts of biological material. Although there are thousands of STR markers that have been identified through genomic research, the FBI has established a standard set of 13 STR locations (or loci) for forensic DNA testing and statistical calculation purposes and are required by the FBI’s National DNA Index System (NDIS). These 13 loci along the DNA molecule are composed of STRs found on 11 different chromosomes and the number of times each STR is repeated at the 13 loci constitutes a DNA profile. This type of forensic DNA testing is the most commonly used method and involves a four-step process – extraction, quantitation, amplification, and detection. Once the analysis is complete, the DNA profile that is generated from a piece of biological evidence can be directly compared to the DNA profile from a reference sample from a victim or suspect to determine whether the person is included or excluded as the source of the biological material. DNA profiles generated from evidentiary items can also be uploaded to the CODIS database and searched against other unknown DNA profiles from other cases as well as compared to DNA profiles of convicted offenders. This is a powerful investigative tool, especially in non-suspect cases. Other types of DNA testing utilized in criminal cases include Y-STR and mitochondrial DNA analysis.
Y-STR analysis is specific to the Y chromosome and detects only male DNA – an invaluable investigative tool when a mixture of female and male DNA is present and the female is the major contributor (e.g., sexual assault cases). However, since the Y chromosome is paternally inherited, every male individual in the same paternal lineage will be expected to share the same Y-STR profile. Because of this, the resulting statistics are not as discriminatory as those typically found in nuclear DNA testing. Y-STR analysis is also used in genealogical DNA testing.
Mitochondria are cellular structures found in all of our cells. They are known as the “power plants” of our body, providing approx. 90% of the energy that body needs to function. Each cell in our body contains hundreds to thousands of mitochondria, each containing several loops of DNA. Therefore, since each cell in our body can have thousands of copies of mitochondrial DNA (mtDNA), mtDNA analysis has become a powerful tool in forensics for identifying human skeletal remains (including bones and teeth) as well as hairs without roots. mtDNA is present in high copy number within cells, is located outside the nucleus, and is maternally inherited. Because mtDNA is maternally inherited, every individual in the same maternal lineage will be expected to share the same mtDNA profile, with a few exceptions (i.e., heteroplasmy). mtDNA analysis is utilized when the quality and/or quantity of DNA from biological evidence samples is insufficient for nuclear DNA testing, which may occur in old, degraded, and environmentally damaged samples. mtDNA analysis can also be used in cases where maternal relatives are the only available source for reference samples (e.g., cases involving missing persons or mass disasters). The results of mtDNA analysis can provide an important link between victim, suspect, and/or crime scene and can conclusively exclude an individual as the source of a mtDNA profile. The majority of mtDNA analysis involves hair evidence where only the hair shaft is present. Because mtDNA analysis is a destructive process that can consume evidence samples, identifying information from hairs and skeletal remains needs to be documented prior to testing. Although mtDNA analysis is more sensitive than nuclear DNA testing, it is also more rigorous, more time consuming, and more expensive. Also, it is important to note that current mtDNA analysis technology cannot effectively distinguish between different sources or quantities of mtDNA. Therefore, this type of testing is not appropriate for evidence containing possible mixed sources of DNA such as fingernail scrapings, female swabs or clothing with semen stains, or items with “touch DNA” such as telephone receivers, door knobs, computer keyboards, steering wheels, car door handles, etc.
c) Bloodstain Pattern Analysis:
Examination of bloodstain patterns to determine the relationship and relevance of these bloodstains to 1) the crime scene, 2) other physical evidence 3) the individuals involved and 4) to the reported facts of the case. Bloodstain pattern analysis involves visual examination and characterization of bloodstains based on their size, shape, and distribution pattern. This analysis can help determine the sequence of actions and events at a crime scene and reveal such information as point of origin of the blood, position and movement of individuals and objects during bloodshed, repositioning of bodies or objects, order of events, etc.
Bloodstain pattern analysis can be performed by re-visiting the crime scene and/or reviewing case information such as 1) police reports, witness statements, forensic reports, and autopsy findings; 2) crime scene diagrams, photographs, and/or videotapes; 3) evidence photographs generated by scene and crime laboratory personnel; 4) the actual physical evidence from the crime scene and from those persons involved in the incident.
d) Laboratory Assessment and Evaluation:
On-site witnessing of laboratory testing of limited evidence samples which includes ensuring adherence to proper protocols regarding evidence handling, serology testing, DNA testing, etc.
e) Pre-Trial Preparation and Trial Consultation:
Review motions and court transcripts, evaluate and assess the scene investigation, examine forensic laboratory testing records, interpret scientific findings, relate technical and scientific information to the reported actions and events in the case, provide recommendations for additional forensic testing, help develop cross-examination questions for fact witnesses and opposing experts, assist with case theory development, provide moot court consultation, help develop voir dire questions of potential jurors, participate in pre-trial interviews of witnesses, provide in-court consultation throughout the trial especially during opposing expert testimony, and provide ideas for closing argument.
f) Expert Witness Testimony:
Direct expert testimony in the areas of forensic serology, forensic DNA analysis, biological evidence collection, forensic biology laboratory protocols, crime scene investigation, crime scene analysis, bloodstain pattern analysis, and criminal profiling.
g) Education and Training:
Instructional seminars on the basic principles, theory, and application of crime scene investigation techniques, evidence collection, forensic serology testing, forensic DNA analysis, criminalistics, bloodstain pattern analysis, and criminal profiling.
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