BBC Focus - 04.2020_

bySIMONCROMPTON

(@Simoncrompton2)

Simonis a science, medical and

health writer

FE ATURE DNA DETECTIVES

HOW ‘SNAPSHOT’ DNA

PHENOTYPING WORKS

• ParabonusesitsanalysisofcrimesceneDNAtopredictthe
  physical appearance and geographic ancestry of a person of interest.


• SNPanalysisofDNAsamplerevealsgeneticvariantsthatcan
  predict:geneticancestry,eye colour, hair colour, skin colour,
  freckling and face shape.


• Eachtraitis givena confidence rating: how likely it is, given the
  strength of genetic markers.


• Thisdatais builtintocomputer-generatedimagesofthecrime
  suspect’sface.A smallstudyfromtheUniversityofTexasfound
  thesevisualpredictionsoffacialfeaturesandancestrytobe
  generallyrecognisable.ButDeniseSyndercombeCourt,professorof
  forensicgeneticsatKing’sCollegeLondon, questions whether the
  representations are robust enough.


• Geneticphenotypingis oftenusedalongsidegeneticgenealogy,to
  narrowdownpotentialsuspectsidentifiedinfamilytrees.For
  example,if a personofinterestis knowntobeAfricanAmerican,
  butDNAphenotypingsuggeststheyarelikelytohavegreeneyes,
  genealogistswillfocusonthe branch of the family tree that has
  most European influence.

“THE UK NATIONAL CRIMINAL

INTELLIGENCE DNA DATABASE,

25 YEARS OLD THIS YEAR, HOLDS

INFORMATION ON AROUND 10

PER CENT OF THE UK POPULATION

AT ANY ONE TIME”

2 to compareagainstonGEDmatch,comparedwith1,000,000

in2018.“It’snowmuchmoredifficulttosolvethesecases

andnarrowthemdownasspecificallyasweusedto,”she

says.“Wedon’thaveenoughdata,whichmeansa lotmore

workhastogointoit.”Investigatorsmayneed to ask certain

linesofdescendantsforDNAsamples.

Thereareotherlimitationsthatmayrestrictexpansion.

ThosewhosubmitDNAtoresearchtheirancestrytendtobe

ofEuropeanextraction– standinginthewayofgrowthin

manycountries.DataprotectionlawsinEuropearegenerally

tighterthantheUnitedStates.Andsomeexpertsbelieve

thereissimplynoneedforgeneticgenealogy in countries

thatoperateaneffectivecrimedatabase.

DeniseSyndercombeCourt,professorofforensicgenetics

at King’sCollegeLondon,saysthattheUKhasn’tgonedown

thegeneticgenealogyroute,partlybecauseit alreadyhasa

databasethatrepresentsa morerelevantpopulation.TheUK

NationalCriminalIntelligenceDNADatabase, 25 yearsold

thisyear,holdsinformationonaround 10 percentoftheUK

populationat anyonetime– becauseit includesDNAdataon

crimesuspectsaswellasthosewhohavecommittedcrimes.

AccordingtoSyndercombeCourt,a complicatedDNA

analysisthatcanidentifydistantcousinsisn’trequiredif your

crimedatabaseis comprehensiveenough.“TheUKdatabase

containsinformationononeineightmalesbetweentheage

of 15and 45 to50,soit’sverypowerful,”shesays.Inthecase

ofunsolvedseriousoffences,DNAcanbecomparedtothis

databaseandit is likelytopickupcloserelatives– parents,

children,fullsiblingsandsometimeshalfsiblingsanduncles.

“TheproblemintheUnitedStatesisthattheyhaven’t

beenputtingtheirfelonsontoanidentifiableDNAdatabase.

Most of these people couldhavebeenpickedupmanyyears

agoif theUnitedStateshada

propergovernancestructure.We

havethat,somyfeelingisthat

thenumberofcasesit wouldbe

usefulforintheUK would be

very limited.”

* IMAGE SHOWS A VOLUNTEER, NOT A CRIMINAL