In March 1990 in Virginia, the body of a young female was discovered in her home. The victim, who had been sexually assaulted and stabbed to death, was 22-year-old Dawn Bruce. Unfortunately the incident scene did not turn up as much evidence as investigators would have liked, with the only piece of evidence that seemed useful being a blood-stained pillow case found adjacent to the victim’s body.
The pillow case was taken to the Forensic Unit of Henrico County Police. Upon close examination of the bloodstains, a faint stain seemed to express ridge details. Furthermore, it was believed that some of the stains appeared to have been transferred from the blade of a knife, even though no knife had been found at the scene of the murder. Investigators focused on the potential fingerprint detail and transferred the evidence to the Virginia Division of Forensic Science in Richmond. 1,8-Diazafluoren-9-one (DFO), which was a relatively new chemical developer at the time, was applied to the bloodstain and then made to fluoresce. After development, the print was photographed. However due to the poor quality of the ridge detail and the disruptive weave of the fabric, the print could not be used to identify the culprit. A relatively new image enhancement technique was used by Hunter Graphic Information Systems in Charlotte, North Carolina to attempt to improve the image of the latent print. Following four intensive hours of treatment, the image was successfully enhanced to the extent that it could be used for identification purposes.
Many individuals were examined throughout the investigation, however the prime suspect was the next door neighbour of Dawn Bruce, Robert Knight. Although his prints were already on record from a previous arrest, they were not rolled far enough for the ridge detail found on the pillow case to be compared, as the scene print seemed to be from the side of a finger. The suspect could not be arrested.
Further evidence was discovered during the post-mortem examination, at which time semen was found on the victim’s leg. The initial serological report provided a match with the suspect, who had a relatively rare blood type. This was enough to issue a warrant. Eventually, on August 7th of that year, a full set of inked fingerprints were compared with the latent print from the pillow, and the left thumb of Knight was deemed to match the crime scene print. In addition to this, results from the DNA analysis later confirmed the identity of the perpetrator to be Knight.
During the trial the defence heavily attacked the image processing used to enhance the print, which was a new technique and so could potentially be dubious. However the court was walked through the entire image processing procedure by experts and the evidence was eventually deemed to be admissible. Well into the trial a new piece of evidence also came to light. A maintenance man working in the defendant’s apartment discovered a knife hidden in a pipe chase. This was consistent with the knife used the attack the victim and the stains left on the pillow, plus traces of human blood were found on the blade.
On 18th June 1991, Robert Knight was found guilty of the murder of Dawn Bruce and given four life sentences
The Power of Physical Evidence: A Capital Murder Case Study. Chesapeake Bay Division International Association for Identification. [online] Available at: [http://www.cbdiai.org/Articles/tiller_8-91.pdf]