3.6 Conclusions
4.3.2 Calibration and Sensitivity
Because anything in the physical universe has the potential of becoming an item of evidence in an investigation, a wide variety of procedures may be used in analyzing and interpreting evidence in a criminal case. These procedures include examining firearms, serological and toxicological tests, examining hairs and fibers, mineralogical and metallurgical tests, and document examination.
3.9.1 Firearms Examinations
Firearms are identified through microscopic imperfections that are produced inadvertently in gun barrels during manufacture. Subsequent use and wear contribute further to a weapon’s individuality. A bullet fired from a pistol or rifle, therefore, has impressed on its surface the individual characteristics of the barrel through which it was fired. Other parts of the gun also possess individual characteristics. The firing pin, breech face, extractor, and ejector come in contact with the cartridge case; hence, cartridge cases may be scared with distinctive markings that can be identified with a particular gun.
3.9.2 Serological Investigations
Serology in its sense is the study of body fluids in relation to sickness and its treatment. In crime detection, serological procedures are applied to the identification of a bloodstain; that is, to determining its human or
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animal origin and its blood-group classification. Suspects in violent crimes often claim that bloodstains on their clothing, weapons, or automobiles have no connection to the crime. Serological tests on dried bloodstains can ascertain whether the blood in question could have come from the suspect or the victim. DNA fingerprinting was deoxyribonucleic acid (DNA), using chemical analysis investigator can determine if blood or other body fluids found at a crime scene match a genetic profile.
3.9.3 Toxicology
Toxicology may be defined as the science of poisons. Special methods of analytical chemistry have been developed for use in toxicological examinations. The problem of separating poison from order materials and of identifying them recurs constantly in a crime laboratory. The specimens ordinarily examined in cases of suspected poisoning are tissue samples from vital organs, blood or urine, food, drink, and suspected poison itself.
3.9.4 Hairs and Fibres
A piece of hair or a few strands of fibre when compared with known specimens may prove valuable in solving a case. For example, a fiber found on a cut screen at the scene of a burglary may be associated with a suspect’s jacket, or a hair found on a suspected car in a hit-and-run case may help prove that the car struck the victim. An examination of hair may reveal whether it is of human or animal origin. If of human origin, it can be compared with hairs from a particular person’s head or body.
3.9.5 Mineralogical Instigations
The science of mineralogy is also used in crime detection. The mineralogist studies soil, plaster, cement, brick, concrete and glass for any evidence. Mineral analyses have shown that differences may be detected in soil composition. Soil and dust found on a suspect’s clothing and determined to be comparable to that at the crime scene help to prove the person’s presence in that locality.
3.9.6 Metallurgical Investigations
Metallurgical examinations make it possible to identify the source of an item whether made of metal, plastic, ceramic, or other material – found at a crime scene, and further, to determine if two similar items were fractured from each other, the nature of the force causing the fracture, the direction from which the force came, and the time when the
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fragments became separated. Metallurgical examinations can also determine how a metal item was manufactured, and whether items found in different locations were made at the same time and by the same manufacturer. Such identification helps trace the evidence to its owner.
The metallurgist can in some cases restore obliterated or altered numbers on metal objective.
3.9.7 Document Examination
Document examination traditionally consisted largely of comparing questioned handwriting with known handwriting to determine the writer’s identity; it also includes the examination of hand printing, e- mail and other digital documents, forgeries, typewriting, inks, paper, indented and eradicated writing , rubber-stamp impressions, charred paper, and related items. No two people write exactly like; the writing process is so complex that personal peculiarities always persist in the handwriting of any given individual. Detailed examination reveals these hidden characteristics, which can then form the basis for an expert’s opinion.
SELF-ASSESSMENT EXERCISE What is Crime Detection?
4.0 CONCLUSION
Criminal investigations are now conducted in the Nigeria at Local Government state and Federal levels in accordance with the dictates of the law. The conduct of an investigation is governed by information obtained from people, records, and physical evidence. Victims or witnesses still provide the bulk of facts as to when, where, how, why, and by whom the crime was committed.
The methods of detection employed are dictated by the nature of the crime and the procedures permitted by the legal system. Most investigations begin with careful, objective observations that are then assembled, collated, and matched against applicable law. If there is reason to assume that a crime has indeed been committed, further investigation is undertaken using scientific methods and techniques.
Technological advances have been incorporates into crime investigation as well; for example, analyzing trace clues such as dust, paint, glass, and other microscopic evidence is now possible.
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5.0 SUMMARY
At the end of this unit, you have learnt (1) What Crime Detection is all about.
(2) What Criminal Investigation is all about
(3) The historical background of Criminal Investigation.
(4) The goals of Criminal Investigation.
(5) The Various methods of Scientific Crime Investigation 6.0 TUTOR-MARKED ASSIGNMENT
(1) Discuss factors that militate against the police in effective crime detection in Nigeria society
(2) Suggest ways in which the police can improve on crime detection in our society.
7.0 REFERENCES/FURTHER READINGS
Bohm, R. M. and K. N. Haley (2002) Introduction to Criminal Justice.
3rd Edition. Glencoe: McGraw-Hill.
Dempsey, J. S. and L. S. Forst (2005) An Introduction to Policing. 3rd Edition. Belmont, CA: Thompson and Wadsworth.
Hess, K. M. and H. M. Wrobleski (2005) Police Operations: Theory and Practice. 3rd Edition. Belmont, CA: Thompson Wadsworth.
Neufeid, P. J (1990) When Science Take the Witness Stand: Scientific America. Beverly Hill, CA: Sage.
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UNIT 3 TRAINING AND RETRAINING IN THE NIGERIA