Summary of concepts Human DNA Analysis and Interpretation

This document contains keywords for concepts of which an expert in the field of DNA should minimally have a basic knowledge.

Forensic biology

  • Sources of DNA evidence
  • Crime scene investigation and laboratory analysis of biological evidence
  • Identification and presumptive testing of body fluids (blood, semen, saliva)
  • Confirmatory assays for body fluid identification (immunoassays)
  • Uncertainty concerning attribution of DNA (particularly at low levels) to specific body fluids

General

  • The structure of DNA and the variability of the human DNA genome
  • Loci, alleles, genotypes and DNA profiles
  • Polymorphisms commonly used for DNA testing
  • The molecular biological basis of forensic DNA tests; using the DNA profile to identify a forensic sample
  • Extraction and quantification of DNA
  • Polymerase chain reaction
  • Short tandem repeats and mutation processes
  • Forensic multiplex STR typing kits
  • DNA separation by CE and LIF detection
  • Analysis of results, including the use of ladders for fragment sizing, use of analytical thresholds and identification of artefacts such as stutter, “pull-up” and identification of mixed samples.

QC/QA

  • Quality control and quality assurance of forensic DNA analysis
  • Laboratory accreditation, personnel certification and proficiency testing
  • Validation studies
  • Laboratory error rates
  • Understanding and minimizing the risk of contamination in the forensic process: methods of reducing the occurrence of contamination and detecting when it has occurred
  • Continuous improvement and quality

DNA statistics

  • Likelihood Ratio (LR)
  • Bayes Theorem
  • Product rule to calculate the probability of independent variables
  • DNA mixture deconvolution and recommended procedures for analysing mixed samples
  • Accounting for relatives, where applicable, in calculating evidential strength
  • Database issues
  • Inclusion criteria and search (im)possibilities of the national DNA database including the detection of false negative and false positive matches
  • Population Genetics
  • Hardy-Weinberg equilibrium/Linkage equilibrium
  • Population Substructure
  • Allele frequencies, genotype probabilities
  • Applying the product rule for independent events
  • Conditional match probabilities
  • Fst/Theta population substructure correction; correction for possible allele dropout
  • Sampling variation in construction of DNA population databases
  • Proper Interpretation of the Evidence
  • Common Logical Fallacies (Prosecution/Defence Fallacy)
  • Evidential strength of database match
  • DNA database search controversy
  • Avoidance of cognitive bias

Minimal traces (Low Template DNA Analysis)

  • Evaluation of potential low template DNA typing results.
  • Allele and/or locus dropout due to degradation, preferential amplification, stochastic effects and stochastic thresholds
  • Replication and consensus DNA profiles
  • Approaches for the statistical evaluation of DNA profiles from low template DNA samples

Y-chromosome Testing

  • Y-chromosome evolution and its consequences for forensic analyses
  • Patrilineal inheritance
  • Laboratory analysis of Y-chromosome STR’s
  • Population genetics of Y-STR haplotypes
  • Use of Y-STR population databases (YHRD)
  • Statistical evaluation of Y-chromosome haplotypes
  • Interpretation of Y-STR mixtures

Kinship DNA Testing

  • Inheritance of genetic polymorphisms
  • Technical procedures for determining kinship
  • Statistical evaluation of kinship (e.g. paternity index, sibling index, Bayesian networks)
  • Incorporation of the presence of mutations and null-alleles in the statistical evaluation
  • Principles of disaster/mass identification
  • Principles of familial searching in databases
  • Use of Y-STR and mtDNA analysis to narrow candidate lists from familial searching in databases

Externally Visible Characteristics

  • Evolution and migration of Homo sapiens
  • Population genetics of externally visible characteristics
  • Principles of determining the geographic origin of an individual
  • Principles of determining externally visible characteristics
  • Knowledge about genes involved in the biosynthesis of melanine (skin and hair pigmentation, iris colour)
  • Technical procedures for determining geographic origin or externally visible characteristics
  • Approaches for the interpretation of genotyping results for determining geographic origin or externally visible characteristics
  • Knowledge of the limitations of determining geographic origins or externally visible characteristics

Mitochondrial DNA Testing

  • Mitochondrial DNA evolution and its consequences for forensic analysis
  • Matrilineal inheritance, variable mutation rates, heteroplasmy and principles for evaluating close non-matching mtDNA sequences
  • Laboratory analysis of mitochondrial DNA (e.g. Sanger sequencing, mini-sequencing)
  • Population genetics of mitochondrial DNA haplotypes
  • Use of mitochondrial DNA databases (EMPOP)
  • Statistical evaluation of mitochondrial DNA matches

Reporting at Activity level

  • Understanding of the principles of case assessment and interpretation (CAI)4 and the necessity for the following criteria: balance, logic, robustness and transparency
  • Formulation and evaluation of appropriate hypotheses
  • Understanding use of data and experience for evaluation of results given activity level hypotheses:
    - Knowledge concerning transfer of cells and DNA (primary, secondary, tertiary)
    - Knowledge concerning persistence of DNA and the impact of e.g. environmental conditions
    - Extensive experience of forensic DNA analysis and interpretation in forensic casework
    - Transparency regarding any limitations of the data used
  • Understanding of the principles of probabilistic (Bayesian) networks in evidence interpretation