The frenetic investigations which followed the October 2001 anthrax letter threats compelled law enforcement to devise new strategies to detect, stop and trace biological pathogens.
The search continues for the perpetrators of the anthrax crimes, but the good news is a new law enforcement discipline, known as microbial forensics, was found in the process.
Microbial forensics combines principles of public health epidemiology and law enforcement to identify patterns in a disease outbreak, determine which pathogen may be involved, and, when possible, trace the organism to its source. Microbial forensics uses the "biological fingerprint" of an infectious organism to help pinpoint the source, giving police and health officials a better chance to respond effectively to a biological threat.
Investigating evidence on the microbial level tends to raise the forensic bar. Since investigators must consider potential prosecution and presentation of minuscule evidence in court, biocrime investigations demand careful controls and standards for validation and evaluation of technologies and the data they produce.
Scientists can easily evaluate new methods of detecting organisms implicated in a bioterrorist attack, but taking the resulting evidence into a court is another matter. Any microbial evidence, such as anthrax spores, that links to a suspect has to meet stern standards.
Here comes the nudge
This is not just a game of scientific publish or perish. More is at stake than academic reputation.
"We're not talking about a jury of your scientific peers. We're talking about lawyers, judges and trial juries," says Abigail Salyers, professor of microbiology at the University of Illinois, and past-president of the American Society of Microbiology. "The consequences are not just having a paper accepted or rejected by a prestigious journal, but rather of sending someone to jail."
Salyers says even if the anthrax perpetrators were caught, it might not be that easy to achieve a conviction, especially if the spores are part of the physical evidence. If tests on the spores found in the suspect's possession were the same DNA signatures as the spores found in the letters, that might mean one thing on the scientific level, but something quite different in court.
"If you took that finding into court, all sorts of questions arise," says Salyers. "What does 'same' mean? Does it have to be 100-percent identical? Even if it is identical, does it really prove that it's the 'same?' "
Salyers sees a couple of big problems pertaining to the presentation of microbial evidence in court.
First, although the technology for doing DNA-based and other molecular analyses is widely used and universally accepted in the research community, the kind of rigorous validation and development of appropriate quality control standards for the use of this technology in forensics is still not well developed.
"Research is under way, but it might still be fairly easy for a defense lawyer to raise questions about accuracy and interpretation, much as happened in the infamous Simpson trial," she explains.
This is not so much due to weaknesses in the technology as it is that scientists have not thought about forensic uses and thus not developed validation and quality control guidelines appropriate for legal application.
The second problem microbial forensics must deal with pertains to the speed at which microorganisms mutate.
To show the strain of bacterium which produced a spore found in a suspect's home or office is the strain used in the anthrax attack, and not a strain that was originally in the soil and tracked into the location, is no problem.
Different strains of Bacillus anthracis differ enough at the DNA sequence level that even a partial genome sequence of the two strains would be sufficient to make the distinction because there would be a number of differences, what microbial scientists call a DNA sequence "fingerprint."