Powerpoint for this web page
Forensic mathematics home page
Spanish-Portuguese ISFG section

Forensic Mathematics slide show talk

presented at La Gomera, Canary Islands, June 3, 1999
Charles Brenner, Ph.D., Consulting in forensic mathematics

Strategies and calculations in DNA kinship cases

Kinship method

Likelihood ratio

What a likelihood ratio is

Likelihood ratio for being French

Data: Subject speaks 100 French words in 1 hour
  • Explanation #1: subject is French
    • 20% event
  • Explanation #2: subject is not French
    • 1% event
  • LR=20; Data is 20 times more characteristic of French person


Likelihood ratio for paternity (PI)

  • PI = X/Y, where
    • X=P(genetic types | man=father)
    • Y=P(genetic types | man not father)
  • Interpretations:
    • Odds favoring paternity over non-paternity assuming all other evidence
    • is equally divided
    • Evidence is PI times more characteristic of paternity
    • What the "exclusion" method is
    • Likelihood ratio for Paternity (PI)
  • Other basic kinship situations
    • Avuncular index (Is the man an uncle?)
    • Other kinship cases
    • Missing person kinship case
  • Other applications of the likelihood ratio
    • Null allele
    • Mutation
      • PI when possible mutation
      • Mutation analysis: concept
      • Paternity case: one "exclusion"
      • Paternity case: two "exclusions"
      • Mutation (old method)
      • Old mutation formula
      • Old mutation formula is
      • Mutation model (old formula)
      • Mutation model (more realistic)
      • Reasonable mutation model, STR's
      • Mutation LR (new, for STR's)
      • STR mutation rates
      • Mutation reference
    • Kinship II (advanced)
      • More than two scenarios
      • Three scenarios –
      • Father/Uncle/Unrelated analysis
      • Likelihood ratios are "transitive"
  • DNA-VIEW software
  • Summary
  • Thanks

Top of page
Forensic mathematics home page