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Forensic DNA analysis is a scientific method used in criminal investigations and legal contexts to identify individuals based on their unique genetic makeup. This type of DNA testing plays a critical role in solving crimes, identifying victims, and exonerating the innocent. Here’s a detailed overview of forensic DNA analysis:

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Features of Forensic DNA Analysis

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  • Unique Identification: DNA is unique to each individual (except identical twins), making it a powerful tool for identification.

  • Biological Samples: Can be performed on various types of biological samples such as blood, saliva, semen, hair, skin cells, and bones.

  • High Precision: Modern forensic DNA analysis techniques offer high accuracy and sensitivity, capable of analyzing even degraded or minute samples.

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Methods of Forensic DNA Analysis

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  1. Short Tandem Repeat (STR) Analysis

    • Purpose: The most common method used in forensic DNA testing.

    • Process: Examines specific regions in the DNA known as short tandem repeats (STRs). The number of repeats varies among individuals, providing a unique DNA profile.

  2. Mitochondrial DNA (mtDNA) Analysis

    • Purpose: Used when nuclear DNA is not available, often in cases involving old or degraded samples.

    • Process: Analyzes DNA found in the mitochondria, which is inherited maternally and can provide information about maternal lineage.

  3. Y-Chromosome Analysis

    • Purpose: Useful in cases involving male lineage or when female DNA needs to be excluded.

    • Process: Examines genetic markers on the Y chromosome, which is passed from father to son.

  4. Single Nucleotide Polymorphism (SNP) Analysis

    • Purpose: Used for more detailed genetic analysis and in cases where STR analysis is not sufficient.

    • Process: Analyzes variations at single nucleotide positions in the DNA sequence.

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Applications of Forensic DNA Analysis

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  • Criminal Investigations:

    • Identifying suspects and linking them to crime scenes.

    • Exonerating wrongly accused individuals.

    • Solving cold cases by reanalyzing old evidence.

  • Victim Identification:

    • Identifying victims of crimes, accidents, and disasters.

    • Assisting in missing persons cases.

  • Paternity and Family Relationships:

    • Establishing biological relationships in legal cases such as paternity disputes and inheritance claims.

  • Human Remains Identification:

    • Identifying remains in forensic anthropology and archaeology.

    • Assisting in mass casualty events and disaster victim identification.

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Process of Forensic DNA Analysis

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  1. Sample Collection: Biological samples are collected from the crime scene, victims, suspects, or evidence items.

  2. DNA Extraction: DNA is extracted from the collected samples using chemical processes.

  3. DNA Quantification: The amount of DNA extracted is measured to ensure there is enough for analysis.

  4. DNA Amplification (PCR): Polymerase Chain Reaction (PCR) is used to amplify specific regions of the DNA to create multiple copies for analysis.

  5. DNA Profiling: The amplified DNA is analyzed to create a DNA profile, which is compared against known samples or entered into DNA databases.

  6. Data Interpretation: Forensic scientists interpret the DNA profiles to draw conclusions about the genetic matches or exclusions.

  7. Reporting and Testimony: The results are compiled into a report, which may be presented in court. Forensic experts may also testify about the findings.

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Considerations

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  • Chain of Custody: Ensuring the integrity and proper handling of samples from collection to analysis is crucial for the admissibility of evidence in court.

  • Contamination: Preventing contamination of samples is essential for accurate results.

  • Ethical and Legal Issues: Handling DNA evidence involves ethical and legal considerations, including privacy rights and the potential impact on individuals’ lives.

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