Non-Paternity: Implications and Resolution

Transcription

1 Non-Paternity: Implications and Resolution Michelle Beckwith PTC Labs 2006 AABB HITA Meeting October 8, 2006

2 Considerations when identifying victims using relatives Identification requires knowledge of how people are biologically related Number of relatives provided Alternative testing methods Average non-paternity in population

3 Why discuss non-paternity? DNA testing identifies a match to ONE of the provided children Biological pedigree given DNA evidence Social pedigree Did we find the remains of or?

4 Siblings Tested What does it tell us about the missing person when these three provided relatives cannot be full siblings?

5 Trying to identify the biological pedigree Most likely you can make the assumption that all children have the same mother (or can you?) Sometimes you can calculate statistics to determine the most likely scenario of the three sibs (half, full, etc.) How does the victim play into the family? How many fathers do the siblings/victim have?

6 One Additional Father 4 more possible combinations with two fathers

7 Two Additional Fathers 3 more possible combinations with three fathers

8 Three Additional Fathers Which pedigree is correct (15 possibilities)? How do you identify the victim?

9 Identification Will you find the victim using the tested relatives? Mitochondrial testing may significantly help Y Chromosome testing may help determine some parts of the biological pedigree

10 Is this a real issue? Family reference data was collected from 127 DNA identified victims of Hurricane Katrina, representing 330 instances of paternity ~14.29%* of victim identifications made my June 1, 2006 were affected by biologically incorrect social pedigrees *MANY DIFFICULT and/or PROBLEMATIC cases were not completed at the time this data was collected. Most of the cases had issues that were due to the inability to determine relationships within the families. The data is skewed with lower instances of non paternity than was truly exhibited due to the time of data collection.

11 Family References Instances of non paternity: ~8.48%* 7.88% confirmed non paternity (26 references) 0.6% suspected non paternity (2 references) *MANY DIFFICULT and/or PROBLEMATIC cases were not completed at the time this data was collected. Most of the cases had issues that were due to the inability to determine relationships within the families. The data is skewed with lower instances of non paternity than was truly exhibited due to the time of data collection.

12 Victim Identifications Identifications affected: ~14.29%* 12.7% confirmed non paternity issues (16 victims) 1.59% suspected non paternity issues (2 victims) *MANY DIFFICULT and/or PROBLEMATIC cases were not completed at the time this data was collected. Most of the cases had issues that were due to the inability to determine relationships within the families. The data is skewed with lower instances of non paternity than was truly exhibited due to the time of data collection.

13 Statistical Considerations When do you modify the social pedigree to perform statistical analysis? How do you statistically take into account the social pedigree being biologically incorrect? Does this change based on how the social pedigree is incorrect?

14 What relatives do we want test? Parents Children and their other parent Full siblings * Half siblings * Aunt, uncles, nieces and nephews * Other biological relatives and/or relevant parents of biological relatives* * Some relatives may require mitochondrial and/or Y-STR testing to identify a potential victim. A pedigree is necessary to determine if the relative is a qualified candidate for either type of testing.

15 Overcoming Unknown Non-Paternity How many family references need to be provided? Does this effect who we choose to test? Minimize the chance of missing an identification with Mitochondrial and Y-STR testing Sometimes it is impossible!

16 Only Living Biological Relatives Mitochondrial is not available Y-STR is not available

17 But there is hope for most cases! Mitochondrial testing on any of the siblings in this case will ensure some type of DNA identification

18 Unique Families All tools and resources must be considered for each case to determine most appropriate course of action Determine family structure by creating a pedigree Determine best family members to test (considering maternal relationships) Identify potential relationship problems Consider personal item availability Is the case resolvable with autosomal STR testing alone? Will the provided family references provide a hit for a victim? Identify alternative DNA testing types (Y-STR, Mito) for specified relationships When in doubt, test everything you can!

19 Acknowledgments Government Agencies FEMA Louisiana Department of Health and Hospitals Louisiana State Police Crime Laboratory Entire Staff at the Louisiana Family Assistance Center NIJ & NIH Sozer, Niezgoda and Associates, LLC Mandy Sozer, Ph.D. New York OCME Tiffany Vasquez Stacey Sainte-Marie Laboratories Bode Technologies Reliagene Technologies Orchid Cellmark International Commission on Missing Persons PTC Labs Identigene DNA Diagnostics Forensic Analytical