|
 The
Grim (Glass
Refractive Index Measurement) is a machine used to
compare glass fragments to see if they match.
For example, a burglar may enter a home by breaking a
window resulting in tiny shards of glass landing on his
clothing. The glass recovered from the crime scene may be
compared with those taken from combings of the suspects
clothing. The fragments of glass are crushed and placed on
a glass microscope slide. A few drops of a special type
of silicon oil is placed on the crushed glass fragments and
then the slide is placed in a heated chamber, known as a
hot stage which is placed under a microscope. This
resulting image from the microscope is fed via a camera attachment,
to a computer. The silicon oil on the slide is heated up
slowly by the hot stage which alters the refractive
index of the oil. When its refractive
index is equal to that of the glass,
the glass fragments become invisible! The computer can
determine better then the human eye at which point the
glass becomes invisible and records the optimum match
temperature. The refractive index is then calculated
from two match temperatures made by the computer. If the
refractive index of the glass fragments found on the
suspects clothing matches that of the broken glass found
at the crime scene, then you have more evidence to
support the case that the suspect was at the crime
scene.
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