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Principles and Practice of Criminalistics
Sidebar 9
The Blood or the Print — Which
Came First?
In the mid-1980s, in a motel in Oklahoma City, a young woman was found dead in the bathtub. It appeared
that she had been bludgeoned where she lay and left to die. Blood was everywhere. Forensic experts from
the Oklahoma City laboratory were called to the scene. One of the things they did was to dust for prints.
A palm print was developed amid a few spatters of blood at the end of the ceramic tub opposite the
victim’s head. In particular, the print overlapped a blood drop about 1 mm square. The
crime scene
technician lifted the print as potentially incriminating evidence, and along with it the blood spot.
The palm print was eventually matched to an employee of the motel. According to the work
schedule, the man had cleaned the room just that morning. Thus, the question became, which was
deposited first, the print or the blood? This was obviously crucial in determining the order of events,
as the print could have been left quite innocently by someone cleaning the room before the blood
was deposited. The answer to this question was particularly critical as the
print was essentially the
only evidence in the case; without it, they had no evidence against the suspect.
The technician who lifted the print immediately formed the opinion that the print was left after
the blood was deposited. However, it was left to a more senior fingerprint analyst to make the final
determination. The examiner formed the same opinion, based on criteria that he believed to be
common knowledge. These criteria included (1) the blood was “cracked,” indicating
that significant
pressure had been placed on it; (2) ridge detail started over the stain (although it did not apparently
traverse the entire 1 mm stain); (3) the presence of fingerprint powder in the cracks of the blood drop
indicated the presence of oils on the stain. When challenged, the analyst could provide no supporting
literature in which these
criteria were established, but said they were taught at an FBI class.
For some poorly articulated reason, the lift, including the bloodstain, was sent to serology. There,
a well-meaning but unthinking analyst consumed the blood spot to determine that it was of human
origin. This, of course, was never in dispute. Fortunately, someone had thought to preserve the print
itself in an excellent photomicrograph before the blood was sampled.
A defense expert was brought in to review the case. He was not convinced that the print was
necessarily deposited
after the blood spatter, and he performed some experiments to test his hypothesis.
He spattered some blood on a ceramic surface and watched it dry. Without any disturbance whatsoever,
it developed a cracked and crazed pattern just as a consequence of drying on this particular surface.
Next, he dusted the spattered bloodstains with fingerprint powder. Without any prints, either under-
neath or on top of the blood spatter, he was able to reproduce a pattern with the same characteristics
as that from the case.
To complete the
experiment, the criminalist then spattered blood on top of previously deposited
prints and also applied prints on top of a fresh spatter pattern. In both instances he could find drops that
either did or did not show the apparently distinguishing characteristics of that in the case. The experiment
clearly demonstrated that one could not reliably determine which came first, the blood or the print, using
the criteria proffered by the Oklahoma examiner. Two examples are shown in the figure.
F
rom
the results of the experiments, he devised a test that he challenged several of his colleagues
to take. All who agreed to take the test felt that they could tell whether blood or a print had been
deposited first. He chose several examples that represented each of the possible test situations, and
included instances in which the appearance of the spatter either supported or did not support
(according to the “generally accepted” criteria) what he knew to be the order of deposition. Of the
five certified fingerprint examiners who took the test, no one had fewer than 10 years
of experience,
and the most senior examiner boasted 25 years of experience in fingerprint examination and com-
parison. The best score was only 80% right, while the worst was 80% wrong — worse than guessing!
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