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Did luminol reveal bloody footprints in the
corridor?
Latent
footprint revealed with luminol
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No. In testifying at the trial, the prosecution's forensic witnesses
could not confirm the presence of blood in any
of the stains they detected with luminol. Moreover, DNA tests strongly indicate that none of the bare
footprints detected with luminol was made with the victim's blood.
Very
probably, the luminol reactions involved a non-blood
substance,
which might have been deposited weeks before the murder. As
explained below, this could have been a household
cleaning product, soil, or a number of other
substances.
What is luminol?
Luminol is a chemical compound that reacts with blood by producing
a blue glow that is visible in a completely dark environment for a few
seconds. It is useful as a forensic reagent because it will
reveal traces of blood that are invisible to the naked eye.
The catch is that luminol also reacts with many substances other than
blood. A scientific article about luminol available
here notes that it can
react with components found in "soils, detergents, bleaches, carpet,
metal objects, tools, plastic panels, wood, and vegetable
compounds." The prosecution's key forensic witness told the court she
can tell by looking at a luminol
reaction whether it involves blood or something else, but
she did not perform any scientific tests to validate this claim. The
article linked above notes that, because
luminol reacts with many non-blood
substances that may be present at a crime scene, "the luminol test must
not be considered sufficiently specific to permit an unequivocal
identification of blood."
DNA test results on the bare footprints
Investigators took swabs of each of the six bare footprints they detected with luminol. These swabs were not tested
to confirm
the presence of blood, but they were subjected to DNA testing, with the
following results:
| LOCATION
|
DNA PROFILE |
| Amanda's room |
Amanda |
| Amanda's room |
Amanda |
| Amanda's room |
Amanda |
| corridor |
none |
| corridor |
none |
| corridor |
none |
These results seriously undermine the prosecution's claim that the bare
footprints were made by someone who tracked
Meredith's blood into the corridor following the murder. In fact:
- Meredith's DNA was not detected in a single one
of the bare footprints revealed with luminol.
- No test was ever performed to establish that
any of these prints were made
with blood rather than one of the many other substances that react with
luminol.
- No comparable footprints were found inside the
room where Meredith was killed.
What about the other stains revealed with luminol?
Along with the bare footprints, three other luminol reactions were
observed at the cottage. Two were stains with no shape description, and
one was described as a shoe print. The shapeless stains were in
Amanda's room and Filomena's room. All were swabbed and subjected to
DNA tests. The stain in Amanda's room showed the DNA of both
Meredith and Amanda. The stain in Filomena's room showed the DNA of
Meredith with a very faint profile corresponding to Amanda. The shoe
print was in the corridor, and it showed the DNA of Meredith and Amanda.
These results are unsurprising for samples taken from the floor of a shared
residence where all kinds of residue got tracked around. As
with the bare footprints, no other test was performed to determine the
presence of blood in any of these stains.
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