The Discursive Production of Uncertainty

DNA `fingerprinting' and other methods of genetic profiling have been used in connection with hundreds of criminal trials in the UK, USA and other nations. These molecular biological techniques are employed by the prosecution (and less often by the defense) to produce forensic evidence. By means of these techniques, selected DNA fragments extracted from a suspect's blood sample or cheek swab are compared with residues of blood, semen, skin, excreta, saliva and hair follicles collected at a crime scene. DNA-profiling evidence has been successfully challenged in a few highly publicized cases, but in the vast majority of cases such evidence has been accepted. The extensive testimony and documentation arising from cases like the 1994-95 double-murder trial of OJ Simpson in Los Angeles enable a close study of how the credibility of experts and their practices is fashioned and undermined in testimony. The arguments by the Simpson defense team delved into the practical contingencies and sources of uncertainty associated with forensic uses of DNA-profiling techniques. These arguments resemble many of the general conceptions of scientific practice within the sociology of scientific knowledge. Indeed, the resemblance is so close that the paper faces an interesting dilemma: what can be said about this case that has not already been said as part of the production and public discussion of its details?