The genealogy detectives: a constitutional analysis of 'familial searching.'(Introduction through III. Acquiring DNA for Trawling as a Search, p. 109-138)

AuthorKaye, David H.


"Familial searching" in law enforcement DNA databases has been pilloried as a step "towards eugenics and corruption of blood" and "lifelong genetic surveillance" that is "inconsistent with a basic pillar of American political thought." Courts have yet to address the issue fully, but several commentators contend the practice is unwise, unjust, or unconstitutional. This Article examines the more significant constitutional claims. It concludes that although kinship matching should not be implemented simply because it is technologically seductive, neither should it be removed from the realm of permissible law enforcement information gathering on constitutional grounds. In reaching this conclusion, the Article describes the logic of kinship analysis; clarifies the nature of partial-match searching; shows how an advanced system of DNA databases could yield additional, accurate leads in the investigation of both routine and high profile crimes; and explains why this system, if properly implemented, is compatible with constitutionally protected interests of both convicted offenders and their close relatives.

CONTENTS INTRODUCTION I. FROM KINSHIP ANALYSIS TO KINSHIP MATCHING A. Kinship Analysis with a Suspect B. Kinship Analysis with a Database: The Two Types of Database Trawls C. The Efficacy of Kinship Matching II. EQUAL PROTECTION A. Racial Discrimination B. Arbitrary Discrimination III. ACQUIRING DNA FOR TRAWLING AS A SEARCH A. The Definition of a Search B. Physical Extraction of a DNA Sample as a Search IV. THE REASONABLENESS OF INNER-DIRECTED AND OUTER-DIRECTED TRAWLING A. The State's Interests 1. Authentication: True Identity 2. Intelligence: Investigative Leads and Exonerations 3. The Reduced Expectation of Privacy B. Database Inhabitants' Interests in Avoiding Outer-directed Trawls 1. "A Blooming Family Tree" a. The desire to keep quiet b. The desire not to know 2. More Markers C. Relatives' Interests" in Avoiding Outer-directed Trawls 1. Sheltering Evidence of Guilt 2. Avoiding False Convictions 3. Being a Suspect 4. Maintaining Spatial Anonymity D. The Unbearable Lightness of Shadow Databases CONCLUSION INTRODUCTION

DNA databases are a darling of the detective's nursery. They began as a curiosity thought to be useful for solving only a few types of violent crimes. (1) Today, they are dazzling devices for enforcing criminal laws from car theft to murder. (2) Computerized matching of the DNA identification profiles from crime-scenes and victims (3) to profiles from known individuals has produced hundreds of thousands of "cold hits." (4)

But some people are never satisfied. A number of scientists have concluded the databases could produce many useful investigative leads if a technique known as kinship analysis were routinely employed. (5) To take their idea to its logical extreme, we can envision a database system constructed to be especially useful for this kind of analysis. Like today's databases, this system would pick out any individuals in the database who are likely sources of crime-scene DNA samples. But the trawling would not stop there. Almost magically, it could lead to identifications of individuals outside the database who left their DNA at crime scenes or on their victims.

Unfortunately, there is a catch. These new leads would point only to very close relatives who are not themselves subject to inclusion in the federal and state databases because they have not been convicted of qualifying crimes. Kinship matching, therefore, has been pilloried as "function creep," (6) "mission creep," (7) "a major privacy intrusion in the life of families," (8) "the worst kind of guilt by association," (9) "genetic surveillance for all," (10) and "lifelong genetic surveillance" (11) that is "inconsistent with a basic pillar of American political thought." (12) And, as if all that were not enough, it has been tarred as "biological determinism" (13) and a step "towards eugenics and corruption of blood." (14)

Although early commentators perceived no fundamental legal barriers to kinship matching (15) and most writing continues to focus on policy arguments, (16) some recent commentary displays more sympathy or support for constitutional objections. (17) The most prominent example is an essay by Professor Erin Murphy entitled Relative Doubt: Familial Searches of DNA Databases, which contends the technique is counterproductive for police practice, unfair, unjust, and of doubtful constitutionality. (18)

This Article provides a more complete examination of the two most significant constitutional issues--the Fourteenth Amendment's guarantee of equal protection of the laws and the Fourth Amendment's protection against unreasonable searches and seizures. (19) These constitutional provisions, I maintain, are not show-stoppers. Kinship matching should not be implemented simply because it is technologically seductive, but neither should be it be taken off the legislative table on constitutional grounds. To reach this conclusion, Part I describes the logic of kinship analysis and how it can be applied to state-of-the-art forms of DNA databases that could yield accurate leads in the investigation of both routine and high profile crimes. It introduces a few standard terms from genetics, presents more neutral terminology than the slightly ominous phrase, "familial searching," and explains how kinship matching differs from the partial matching the FBI allows in the national database (NDIS) that is part of the Combined Offender DNA Index System (CODIS). It also discusses the difficulty of measuring the efficacy of "familial searching."

Parts II through IV analyze the two main constitutional objections to kinship matching. Part II argues the practice is clearly compatible with the established understanding of the Equal Protection Clause. Parts HI and IV analyze the interests of all convicted offenders and their families to show why kinship matching in law enforcement databases can qualify as a reasonable search or seizure under the Fourth Amendment. Like every other investigative technique, it can adversely affect very close relatives, but the actual Fourth Amendment interests of the individuals in the database and their close relatives in keeping the state from finding investigative leads from crime-scene DNA are weak. The government interest in efficiently investigating crimes with a thorough and properly implemented system of kinship matching therefore outweighs these interests.


    Kinship analysis refers to comparing DNA from different individuals to see if those individuals might be related. It is done frequently in child support (20) and immigration (21) cases and in missing persons and human remains investigations. (22) It is done in criminal cases when a rape victim has a child or an aborted fetus. (23) It is one reason to believe U.S. soldiers killed Osama Bin Laden rather than a man who merely resembled him. (24) These applications are uncontroversial.

    To appreciate the more controversial use of the procedure in criminal database trawls, it is important to understand the scientific and statistical principles behind kinship analysis. These are straightforward, but a few technical details bear heavily on the procedure's efficacy and invasiveness. This Part, therefore, defines and briefly describes the types of chromosomes, alleles, and loci used in forensic DNA identification and how these generate likelihood ratios for specific genetic relationships between individuals that can be used to produce investigative leads. (25)

    Chromosomes. In humans, DNA comes in packages known as chromosomes. Each cell nucleus normally contains twenty-three pairs of chromosomes. (26) In twenty-two of these pairs, called autosomes, the two chromosomes are about the same length. (27) The twenty-third pair differs between males and females. (28) Females have two copies of the X chromosome, while males have one X and one much smaller Y. (29)

    Sex cells (eggs and sperm) are exceptional in that they have a reduced number of chromosomes. (30) Each sex cell contains only one chromosome from each homologous pair, chosen at random, giving them a total of twenty-three individual chromosomes. (31) When a sperm and egg cell combine, a new set of twenty-three pairs is formed. (32) The fertilized cell divides, as do its daughter cells, giving rise to trillions of cells in the offspring. (33) All the new cells (except for sex cells) have the same genome of twenty-three homologous chromosomes. (34) One member of each pair has been inherited at random from one parent, and the other member was inherited at random from the other parent. (35)

    Loci and alleles. The DNA in a chromosome can be thought of abstractly as a string of four letters (chemical "base pairs"), designated A, T, C, and G. (36) The sequence of base pairs in a particular chromosome (number 16, for example) is mostly the same from one individual to another, but at some locations the sequences are different. (37) The sequence at each location, or "locus," is called an "allele." (38) The simplest alleles are a substitution, deletion, or insertion of a letter at a particular locus. (39) Such variations in the DNA sequence of the same chromosome in different people (or between the paired chromosomes in the same person) are "single-nucleotide polymorphisms," or SNPs. (40) Another kind of polymorphism is a variation in the length of a region of DNA that arises from different numbers of several short, repeated letters. (41) For example, one chromosome number 16 in one individual might have the sequence GATA repeated eight times at a particular locus. Another chromosome 16 might have ten repeats of GATA. Short-tandem repeat, or STR loci, thus resemble trains with different numbers of boxcars. There are other kinds of sequence variations, but STRs currently are the most popular loci for identity and kinship testing, and SNPs are expected to come...

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