The Use of the Spectrograph in Criminal Investigation
| Published date | 01 July 1938 |
| Author | F. H. Newman |
| Date | 01 July 1938 |
| DOI | 10.1177/0032258X3801100308 |
| Subject Matter | Article |
The
Use of the Spectrograph in Criminal
Investigation
By PROFESSOR F. H. NEWMAN, D.Sc.
University College, Exeter
IN
many forensic investigations the amount of material
available is so very small that a complete chemical examina-
tion is not possible; it is insufficient to give any of the ordinary
tests. Recent advances in the science of spectroscopy have
made its application to problems of especial value in such
circumstances. With the modern spectrograph one may
analyse the residue from a single drop of tap water (although
the residue weighs
but
the
j.ccoth
part of a grain) and deter-
mine with fair accuracy the proportions of sodium, calcium,
magnesium and other elements. One can also determine the
major elements in a piece of alloy or counterfeit coin, even
those present to the extent of only one part in a million, and
one can detect in the blood the traces of aluminium absorbed
from a single meal of some food containing only a customary
amount of alum. Used in conjunction with a special type of
photometer, one can ascertain not only that the drug separated
from some toxicological material is morphine,
but
also deter-
mine approximately the quantity separated. So one might
continue to give examples,
but
those quoted above will suffice
at this stage to indicate that the spectrograph in skilled hands
is a valuable implement in criminal investigations.
The
science of spectroscopy is an old one, dating from the
days of Newton, who found that when sunlight, or indeed any
white light, is passed through a glass prism, the constituent
colours of the white light are separated, and a range of colours,
varying gradually from red at one end to violet at the other,
emerge from the prism. This is called a spectrum and can be
exhibited by allowing the emergent light to fall on a white
343
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