Supplement to Chapter 14:

DNA Typing: Lingering and Emerging Issues

Copyright 2001 DH Kaye

In General

The history of DNA evidence is recounted in an engaging book, And the Blood Cried Out by a former prosecutor, Harlan Levy. For a less sanguine view of that history, see Paul C. Giannelli, The DNA Story: An Alternative View, 88 J. Crim. L. & Crimin. 380-422 (1997).

The current scientific and legal issues are discussed in 3 Modern Scientific Evidence: The Law and Science of Expert Testimony ch. 25 (David Faigman et al. eds., 2002), which is a revision of David H. Kaye & George Sensabaugh, Reference Guide to DNA Evidence, in Reference Manual on Scientific Evidence (Federal Judicial Center ed. 2d ed. 2000).

"DNA dragnets": Geographic and other screening

Insert the following after the news story on "mass DNA screening" in Britain (p. 223):


Police in the United States have followed the British example of collecting DNA from large numbers of "volunteers" in the hope of turning up leads -- a practice that has been criticized as "DNA dragnets." [Give examples and discuss legal issues. See PBS religion and Ethics story on Charlottesville]

On the constitutionality of mass screening of members of a single race, see Brown v. City of Oneonta, 221 F.3d 329 (2d Cir. 200), and 235 F.3d 769 (2d Cir. 2000) (opinions accompanying denial petition for rehearing en banc).

There have been suggestions that acquiring blood samples from suspected terrorists (or others) to see whether they have antibodies to anthrax might be useful:

Nicholas Wade, Single-spore Theory of Anthrax Disturbs Investigators, N.Y. Times, Nov, 8, 2001

NEW YORK - Investigators assigned to the case of Kathy T. Nguyen, the Manhattan hospital worker who died of inhalation anthrax last week, are confronting some disquieting possibilities as to how she may have become infected.

One, which has aroused keen interest among investigators, is that at some point in her well-ordered, fairly restricted life, she crossed paths with a perpetrator of the attacks and his product. If that is the case, reconstructing Nguyen's movements, as investigators are trying to do, may lead to the source of the spores.

But another possibility, more threatening to the public, is that Nguyen came nowhere near the person who distributed the spores or an envelope filled with them, and yet was infected anyway. If that is the case, some people may be infected by doses of anthrax spores that are much smaller than generally thought, and Nguyen may have been felled by a very few spores that she somehow happened to inhale.

Except for Nguyen, those who have contracted anthrax have had some obvious point of contact with the spore-laden letters and can reasonably be assumed to have inhaled a significant dose of spores.

But this is not the case with Nguyen. Nothing in her home or mail or place of work at the Manhattan Eye, Ear and Throat Hospital contained any trace of anthrax spores, investigators say.

Dr. Jeffrey Koplan, director of the Centers for Disease Control and Prevention, said Wednesday, "It would take a lot more than a few spores to cause exposure anthrax." And New York City investigators had previously said they were looking for opportunities Nguyen might have had to come in contact with a large quantity of spores.

But some experts believe that just a few spores, maybe even a single spore, can infect a susceptible person in rare circumstances.

Could Nguyen have breathed in a stray puff of spores wafting through Manhattan's canyons? The lethal dose for anthrax is often said to be 8,000 to 10,000 spores. But that is in fact the amount needed to kill 50 percent of a population of monkeys. No one knows the smallest number of spores it would take to kill just 1 percent of a population -- the experiment would require hundreds of monkeys -- but it could be just a couple of hundred spores.

Human lungs hold 500 million miniature compartments where the blood exchanges gases with the air. Each of the 200 spores is likely to be inhaled into a different compartment and would have an independent chance of infecting the body, said Dr. Matthew Meselson, a biologist at Harvard University. In his view a single spore has a chance, however small, of infecting someone.

The Army's chief infectious disease specialist in the Persian Gulf War, Dr. Craig E. Smith, agreed.

The idea that one spore can suffice for infection is somewhat at odds with the view often expressed by officials at the Centers for Disease Control and Prevention that there is a threshold, or cutoff number of spores, below which no infection can occur. But the one-spore theory would make more understandable a case like Nguyen's, in which no obvious route of exposure has yet come to light.

"Should we be alarmed that she's an outlier for whom no obvious connection exists?" asked Dr. Smith, who is now at the Phoebe Putney Memorial Hospital in Albany, Ga. "I do find that alarming because it implies she had a very small inoculum."

Another possible explanation for Nguyen's case is that she passed near some so far unidentified source of anthrax, like a house, office or laboratory where the anthrax spores used in the two attacks were being prepared. If the anthrax was home-grown, the responsible person is presumably someone well trained in medicine or microbiology or pharmaceutical manufacturing.

Dr. Smith said that one way of finding such a perpetrator would be to test suspects' blood for antibodies to anthrax. People brewing anthrax spores are likely either to have vaccinated themselves beforehand, or to have become sufficiently exposed to have raised antibodies even if they were taking antibiotics as protection, another expert said.

"If I'd taken 100 people into custody as potential terrorists, I would have taken a blood sample from every single one," Dr. Smith said. "If anyone came out positive that would mean they had had a natural exposure to anthrax or had been vaccinated, which I think would be evidence they had a premeditated plan to disseminate anthrax."

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said that testing suspects, like those being detained by the FBI in connection with the Sept. 11 attack, "is certainly something that is quite reasonable to consider."

"The presence of antibodies to anthrax," he added, "might indicate if these individuals had been vaccinated to protect them."

There is no sign so far that the FBI has considered screening suspect populations for the presence of anti-anthrax antibodies in their blood. An FBI spokesman dismissed the issue as "a medical question."

Federal investigators did not use the precise methods of blood testing, but instead relied on a far more subjective approach, handwriting analysis, to explore the possible connection of a man from Hamilton Township, N.J., to the three anthrax letters.

Many of the people being detained by the FBI are being held on alleged violations of immigration law, but legal experts said they had not heard of blood samples being requested from the detainees.

"I am not aware of that," said Lucas Gutentag, director of the immigrants' rights project at the American Civil Liberties Union. But he said that, given the secrecy surrounding the investigation, "Even seeking a court order to seek a blood sample would not necessarily be disclosed and could be conducted in a closed judicial proceeding."

Widespread screening of suspect populations, like the detainees, or people on the mail-collection route of the Trenton post worker who contracted anthrax, or any group that Nguyen might have met, would raise legal issues, and even a voluntary request for blood might be seen as coercive. Wide screening with DNA fingerprinting has been used occasionally in Britain.

Dr. Michael Osterholm, a bioterrorism expert at the University of Minnesota, said it was important for investigators to keep their minds open to all possibilities. Nguyen's case was "an epidemiologist's nightmare," he said, because she lived alone with few close contacts and died before she could be interviewed. This clueless landscape was made even harder to read by the long incubation period of anthrax spores, Dr. Osterholm said.

Databanks (p. 226, notes 1 & 2)

Uniqueness (p. 233, note 2)

Using DNA to extend the statute of limitations

Interesting Nonforensic Applications of DNA Typing

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