Compare and contrast the terms Paternity Index (PI) and Combined Paternity Index (CPI). How does each contribute to paternity determination?

Verified step by step guidance

1. Define the Paternity Index (PI) as a likelihood ratio that compares the probability of observing the genetic evidence if the tested man is the biological father versus if he is not. It is calculated for each genetic marker separately.
2. Explain that the Combined Paternity Index (CPI) is the product of all individual Paternity Indices across multiple genetic markers, providing an overall likelihood ratio that summarizes the genetic evidence from the entire DNA profile.
3. Discuss how the PI helps evaluate the strength of evidence at a single locus, indicating how much more likely the tested man is the father compared to a random man from the population for that specific marker.
4. Describe how the CPI integrates information from multiple loci to increase the accuracy and reliability of paternity determination, as combining multiple PIs reduces the chance of coincidental matches.
5. Conclude by explaining that both PI and CPI contribute to paternity determination by quantifying the genetic evidence, where a higher CPI indicates stronger support for paternity, often used alongside statistical thresholds to make legal or clinical decisions.

Key Concepts

Paternity Index (PI)

The Paternity Index (PI) is a likelihood ratio that compares the probability of observing a child's genetic marker if the tested man is the biological father versus if he is not. It is calculated for each genetic locus and reflects the strength of evidence supporting paternity at that specific marker.

Combined Paternity Index (CPI)

The Combined Paternity Index (CPI) is the product of individual Paternity Indices across multiple genetic loci. It aggregates the evidence from all tested markers to provide an overall likelihood ratio, offering a more robust and reliable measure for paternity determination.

Role of PI and CPI in Paternity Determination

PI and CPI quantify genetic evidence to assess paternity. While PI evaluates each locus separately, CPI combines these to strengthen conclusions. High CPI values indicate strong support for paternity, aiding legal and forensic decisions by providing statistical confidence.