The Relationship Between Forensic Medicine and Genetics

Use of Genetic Techniques in Forensic Medicine

DNA Profiling

DNA profiling is a technique that analyzes distinctive features of an individual’s DNA sequence to identify them. It is used in situations such as:

• Criminal Investigation
  Analyzing biological samples like blood, saliva, hair, or skin collected from crime scenes to help identify perpetrators.
  Comparing the DNA profile obtained from the crime scene with profiles in databases of suspects or known offenders.
  
• Paternity Testing
  Comparing DNA profiles of parents and children to confirm parent–child relationships or resolve inheritance issues.
  Typically uses STR (short tandem repeat) analysis.
  

STR (Short Tandem Repeat) Analysis

STR analysis is the main method in forensic DNA profiling, featuring:

• High Variability
  The number of repeats varies between individuals, providing exceptionally high discriminatory power.
  
• PCR Technology
  PCR (polymerase chain reaction) is used to amplify specific STR markers and detect them via fluorescent labeling.
  
• Applications
  
  • Identifying perpetrators from crime scene samples.
    
  • Paternity testing and genealogical investigations.
    

Mitochondrial DNA (mtDNA) Analysis

mtDNA is maternally inherited, meaning that it remains identical from mother to child. Useful for:

• Analyzing Degraded or Old Samples
  Effective in extracting DNA from long-preserved or degraded samples.
  
• Identifying Unknown Individuals
  Used for identifying unidentified bodies or missing persons.
  

Y‑Chromosome DNA Analysis

The Y chromosome is paternally inherited, so father and son typically share the same Y‑chromosome markers. Useful for:

• Confirming Male Lineage
  Especially useful in father–son or brother–brother relationship confirmations.
  
• Specific Criminal Investigations
  Assisting in perpetrator identification using male-specific genetic information.
  

SNP (Single Nucleotide Polymorphism) Analysis

SNP analyses examine single-base variations in the genome and are useful for individual identification and paternity testing:

• Widespread Distribution
  Because SNPs are widely distributed across the genome, they provide additional discriminatory power.
  
• Applications
  
  • Genetic studies related to disease.
    
  • Identifying individuals from crime scene evidence.
    

DNA Databases

• Offender Databases: Store DNA profiles of known offenders and compare them with DNA from new crime scenes.
  
• Missing Persons Databases: Store DNA information of missing persons or unidentified remains, and compare it with DNA provided by family members.
  

Importance of Genetic Techniques in Forensic Medicine

Genetic techniques play vital roles in forensic science for several reasons:

• High Precision and Reliability: DNA profiling is extremely accurate, with minimal risk of misidentification, making it strong legal evidence.
  
• Speed of Results: Methods such as PCR and next-generation sequencing (NGS) allow for rapid results.
  
• Broad Applicability: Used for criminal investigations, identifying individuals, paternity testing, and locating missing persons.
  

Who Are Genetic Specialists or Genetic Counselors?

• A clinical geneticist in Japan is a medical specialist qualified to engage in genetic diagnosis and care.
  
• Certification is administered jointly by the Japanese Society of Human Genetics and the Japanese Society of Genetic Counseling.
  

Summary

In forensic medicine, genetic technologies are indispensable tools for solving criminal and legal cases. Techniques such as STR analysis, mtDNA and Y‑chromosome DNA analysis, and SNP analysis each offer specific advantages, delivering high-precision results. These advances bolster the fairness and credibility of judicial processes, contributing to societal safety and security.