A woman claims one man is the father of her child. But he says he's never met her.
In a classic mystery, Sherlock Holmes or Perry Mason might have solved this paternity suit by matching eye color, or tracing social patterns. But they might have solved more cases if they only knew what students in a new class are learning.
The new course, offered by Medical School Associate Professor of Pathology Dr. Frederick R. Bieber, a medical geneticist at the Brigham and Women's Hospital, explores the scientific principles behind controversial techniques such as DNA typing, also known as DNA fingerprinting, and drug screening, which are introduced into the courts as evidence every year.
"As scientists, we act as advocates for the truth," says Bieber, who teaches Biology E-190, "Principles of Forensic Science," offered through the Extension School. "Attorneys must naturally be adversarial, because they either win or lose."
One of the most controversial topics covered in the course is "DNA typing," a method to identify a person on the basis of genetic information.
"It is a misconception that forensic genetics is only used to restrict freedom and convict people," says Bieber, who says that courses on this increasingly important field are rare. "Its use often results in exoneration of those falsely accused or incarcerated."
For example, he says, such techniques are used in paternity suits, inheritance cases and even in the military. The actual science behind gene typing iscomplex, and highly studied. But the scientificcommunity is currently debating whether DNAevidence is accurate enough to be admitted incourts. Gene typing can be thought of as functioning inthe reverse way of physical fingerprinting, thatis, to eliminate what appear to be matches. Ingene typing, DNA samples isolated from tissues arecompared to information in a computer databank todetermine how rare a particular gene is in thegeneral population. A so-called "match frequency" describes thelikelihood that the sample could have come fromany random individual. As match frequencyincreases, the identification of a suspect becomesless certain. Professor of Biology Daniel L. Hartl is onescientist who has problems with the use of DNAtyping as evidence. In an influential 1991 articlein Science which he co-wrote with AgassizProfessor of Zoology Richard C. Lewontin '50,Hartl argues that DNA typing currently has twomajor flaws. First, he argues, the current DNA databank istoo small, and second, it is unclear how muchattention should be paid to ethnicity whenmatching samples. "Gene frequency differs from subpopulation tosubpopulation," says Hartl. "When you startcomparing with a databank containing DNA types ofall ethnic groups [put together], the matchfrequency seems smaller than it actually is." "[DNA typing] is so good a method for gettingscientific evidence that we shouldn't fudge thestatistics," he says. The National Research Council (NRC), in a bookcalled DNA Technology in Forensic Science,proposed a "ceiling method" to get around theproblems with the process. According to NRCguidelines, any sample which matches the generalpopulation's gene pool more than 10 percent shouldnot be considered a conclusive match. "The ceiling principle, as advocated in the NRCreport, makes a reasonable attempt to solve theproblem of population substructuring," saysBieber. "However, it must be stated that thisprinciple has no basis in mathematical theory orpractice." "Laboratory methods and statistical analysiswill continue to improve. That notwithstanding, nodata base will ever be perfect," Bieber says. "Itwould be regrettable not to use the technologyavailable when there is so much at stake both forthe falsely accused and victims, as well as inother civil cases." Hartl says today that he also supports the"ceiling" as a temporary solution. But also hecriticized those scientists who are satisfied withit as a permanent standard. Andrew Silverman, staff counsel at the StatePublic Defenders' Office, also has reservationsabout using gene typing methods. While he admitsthat DNA typing has proved to be useful in court,he expresses concerns about the reliability of theevidence and the often enormous weight attached toit. "Sometimes, the attacker's identity is the onlyissue disputed, so DNA typing can be the ultimateevidence," Silverman says. "But, a [DNA] matchcan't establish consent or even penetration [inrape cases]." Silverman cautions against the use of the term"DNA fingerprinting" as opposed to "DNA typing."He says that though DNA may differentiate eachperson just as fingerprints do, the typing onlycompares certain genes which may not vary toomuch. Massachusetts determines the admissibility ofscientific evidence by asking whether a given testis generally accepted by the relevant scientificcommunity. And Congress is currently debating abill which would create guidelines for thetechnique. As of today, Silverman contends that DNA typingdoes not fit this criteria, and admission of DNAevidence must continue to be judged on a case bycase basis. "Unfortunately, this may be an instance whenthe court rushed to welcome technology withoutchecking [its] adaptation in the criminal justicearena," said Silverman. But some scientists view protests such asHartl's as unnecessary. David H. Bing, thescientific director of CDR Laboratories, a privatefirm which handles approximately 200 cases peryear involving genetic evidence analysis, saysthat scientists must find a middle ground in theDNA typing debate. Eighty percent of his company's clients, Bingsays, represent the prosecution, with theremaining 20 percent representing the defense. Feerange between $5000 and $50,000 per case. "There are always people who don't like thetest and then there are people on the otherextreme," says Bing. "We in the scientificcommunity are moving toward a consensus."
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