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DNA and police files

DNA fingerprinting is seldom out of the news. In the US itsforensic applications fuel continued controversy. Last weeksaw two developments in the UK. Confirmation by DNAtests of the fate, in Russia in 1918, of the last tsar is ofhistorical interest. More important are some proposalswithin the report of the Royal Commission on CriminalJustice, published in London on July 6. DNA based

identity testing is probably the most significant develop-ment in forensic science since fingerprinting itself, creatingthe possibility of uniquely identifying an individual from asingle cell left at the scene of a crime. In the RoyalCommission proposals are changes to the law on provisionof samples by people suspected of serious arrestableoffences. Samples would be intimate (eg, blood and semen)or non-intimate (plucked hair and saliva). A redefinition ofthe term "serious arrestable offence" and a re-classificationof offences for DNA sampling are also recommended. A keyproposal is that the police be allowed to take non-intimatesamples without consent even where DNA evidence is notrelevant. The fate of these samples would depend on thefate of the suspect. If he or she is convicted, data derivedfrom the sample will be deposited in a national database forfuture use. If the person is not found guilty the informationwill be deposited anonymously, for statistical purposes, in adatabase supervised by an independent body. (Similarprovisions to those regarding the taking of samples alreadyapply in Northern Ireland and seem not to have causedmajor problems. There is no classification of samples intointimate and non-intimate under Scottish law, and anyamendment to the Police and Criminal Evidence Act 1984would not apply to Scotland.)

I see no important distinction between requiring a salivaswab or hair follicle and demanding a fingerprint. Both cangive the same type and quality of information, and in manyways they are both subject to the same types of abuse. Theproposal I have most difficulty with is the database forstatistical purposes based on samples taken from suspects inserious arrestable offence cases. The motive is admirable.In the early days of DNA fingerprinting odds againstchance matches were quoted in terms which were almostmultiples of Avogadro’s number. These estimates werederived by multipying other estimates together and havebeen disputed on the basis of non-random distribution ofalleles. To have accurate figures about probabilities of arandom match between two DNA fingerprints it is essentialto have statistics on real populations. The switch to usingso-called single locus probes simplifies the collection,storage, and analysis of such data but so far these databasesare small (about 300 to 1000 individuals). Much greaterconfidence could be obtained with larger numbers and withregional and ethnic subgroups allowed for.

Setting aside for the moment the civil rights issue would areasonable database result from these proposals? I suggestnot. The police may well have a tendency to arrest peoplefrom certain racial groups in numbers disproportionate totheir representation in the population. When entereddirectly into the database these figures could have somecurious effects if allele distributions differed from those ofthe overall population. For members of an over-

represented racial group there would appear to be an

artificially higher possibility of a random match and in thecase of suspects in under-represented groups an apparentlylower possibility of a non-random match. This could be

corrected by sorting the samples but then there would be aserious risk of anonymity being compromised. The peoplefirst recording the data would be the police and it is theywho would be charged with deleting the name to restoreanonymity. For safety’s sake the donor’s identity shouldnever be recorded.

Although there are attractions to a captive source ofsamples would it not be better to have a well-designeddatabase with some information on the individual samples?This would provide some of the necessary structure to makesuch a database useful not only for the police but also foracademic and medical purposes. It would amount to acensus of genetic variability and could be gathered in a wayless threatening to civil rights than the one proposed by theRoyal Commission. Such a database would not be free fromall potential danger but it would not generate fears aboutcivil rights if it lay outside the police or forensic sciencelaboratories, in, say, an academic institution with experi-ence of confidentiality, quality control, and resistance tooutside interference.

Howard Cooke

MRC Human Genetics Unit, Western General Hospital, Edinburgh, UK

Conscious but paralysed: releasing thelocked-in

"It is as much of the business of a physician to alleviate pain and tosmooth the avenues of death, when unavoidable, as to cure

diseases"—o/:M Gregory, 1725-73

To be fully conscious but able to move only the eyes is apowerful image of horror. Dumas so portrayed MonsieurNoirtier de Villefort in The Count of Monte Cristo, and Zolahad Madame Raquin "buried alive in a dead body". Bothcharacters lived in an age when their ventral pontine lesion,which is usually vascular, would have killed them quickly.Medical technology now can achieve long survival in such a"locked-in" state-a 27-year history of this condition hasbeen recorded.1 Should doctors comply when locked-inpatients, communicating with eye movements, ask thattheir life support be terminated?

Similar difficulties arise with more gradually evolvingdisorders such as motoneuron disease, in which artificialventilation and feeding gastrostomy may delay a patient’sdeath for years in a progressively de-efferented state. Dopatients not have the right to decide to forgo such horrors?Do not others have an equal right to choose to delay a whilein a irrecoverable paralysed state? Furthermore, in somepatients ventilatory support, maybe with a cuirass at night,can be welcomed for symptomatic control rather than lifesupport.2 In a survey from northern Illinois, less than 10%of patients with motor neuron disease were offered andchose long-term ventilation at home. Most of the acceptorsdid not regret it although one in six subsequently asked forventilation to be withdrawn. 3

Other, perhaps easier, issues of treatment withdrawalhave been clarified. Patients who have been carefullyassessed as having irreversibly lost all brain function areregarded as dead and the machines are withdrawn. Braindeath has replaced the medieval concept that a beating heartdefines life. Withdrawal of life-support from patients in apersistent vegetative state, with irrevocably lost cognition