PAPER No.1: General Forensic Science MODULE No.22: Importance of Information Physical Evidence Reveal

Transcription

1 SUBJECT Paper No. and Title Module No. and Title Module Tag PAPER No. 1: General Forensic Science Evidence Reveal FSC_P1_M22

2 TABLE OF CONTENTS 1. Learning Objectives 2. Introduction 3. Criminal Investigation 1. Crime Scene Investigation and 2. Laboratory Investigation 4. Crime Investigation and Evidentiary Clue Materials 5. Scope of a Forensic Investigation 6. Information The Physical Evidence can Reveal 7. Summary

3 1. Learning Outcomes After studying this module, you shall be able to know about: The significance of Physical evidence and their scope The type of information which can be revealed by physical evidences 2. Introduction Forensic sciences being important factor of the criminal justice system plays a vital role in providing scientific information through the analysis of physical evidences to the investigator. The evidences which are present at the crime scene are called Physical-evidence, analysis of which helps in linking the criminal, victim with each other and with the crime scene. It is mainly concerned with the identification of traces of evidence left at the scene, their scientific analysis in the lab and finally reconstruction of events. During an investigation, forensic evidences are recognised, collected from a crime scene and analyzed scientifically in the laboratory according to the requirements of the investigative officer. After that the report is submitted to the court of law. As each crime scene is unique and each case presents its own challenges, Complex cases may require the collection, examination of a large number of varied evidences. These kinds of considerations need to be kept in mind, while evaluating the value of associative physical evidences for comparisons. In this module a specific kind of physical evidences has been introduced and the type of information they reveal has been discussed in detail. Different methods and approaches have been applied to identify these evidences.

4 Physical Evidence This is evidence that does not forget. It is not confused by the excitement of the moment. It is not absent because human witnesses are, it is factual evidence, physical evidence cannot be wrong, it cannot perjure itself only its interpretation can err. - Paul L. Kirk, Criminal Investigation Aim of conducting criminal investigations scientifically means to recognise the evidences at the scene of crime which can be analysed scientifically in the forensic science laboratory and help answering the questions posed by the investigating officer and help to identify the suspected person who has committed the crime. To achieve this aim, the investigation need to be conducted at the following two places 1. Crime Scene 2. Laboratory Both the places are very important but crime scene investigation is more important than laboratory investigation in the sense if at first instance the evidences are properly recognised, collected and packaged properly then only the laboratory results will be useful in the identification of the suspect.

5 1. Crime scene Investigation: The success or failure of the application of forensic science in processing a criminal case mainly depends upon the crime scene investigation only if The physical evidences to be collected from crime scene has been searched and recognized properly The exact position/location of the evidences collected from the crime scene has been recorded. Proper procedure has been adopted to collect and pack evidentiary material at the crime scene Proper control samples from appropriate location for analysis and interpretation purposes has been collected Sufficient quantity of sample has been collected which are required for scientific analysis The samples are collected without contamination. The evidence can be helpful in linking the crime with the criminal on the basis of the results produced by the laboratory. Besides these, another important point which have to be kept in mind while sending samples to the laboratory is to attach a list of queries along with each and every sample sent for analysis to the laboratory. So that only required analysis of each and every clue materials may be conducted and desirable results helps in the identification of suspects.

6 BE CAREFUL The crime scene and all the evidence left at the scene are affected by the external conditions like sunlight or other factors such as rain, wind or snow, may all alter the crime scene with the passage of time and destroy evidence. The moment objects are considered as physical evidence, it became a mute witness to the crime. Investigators must move quickly to identify and protect evidence before environmental effect begins to alter its appearance and composition. 2. Laboratory Investigation: The samples are received in the laboratory for analysis and success of the analysis made in the laboratory depends upon- Whether the proper samples have been sent properly packed from crime scene? Whether the list of queries has been attached with every sample to be analysed in the lab? Whether Materials are identified and compared with the help of prior standardised scientific methods and techniques Whether the results obtained from the analysis are interpreted properly to produce an elaborate and to the point report? And finally whether the report prepared to be presented in the court of law have Simple language understandable to the members of Jury Less use of technical jargon and Photographs and other means to authenticate the results obtained, so that even a layman can understand and appreciate the results produced from the analysis of evidentiary clue materials.

7 Scientific analysis of the clue material helps in establishing the presence or absence of a link between the crime, the criminal, the victim and the place and the time of occurrence. 4. Crime Investigation and Evidentiary Clue Materials Crime scene investigation is a process that aims at recording the crime scene as it is first encountered and collecting all scientific, potentially relevant physical evidences to provide solution in a particular case. The evidentiary clue materials are received in the laboratory might be very diverse in nature, but the methods used to analyze them some times can have a great deal in common or some time may even be identical. Similarly, various types of patterns are also analyzed and interpreted primarily to provide assistance to reconstruct (sequence of steps) the crime, although the patterns may have been produced by quite different events involving quite dissimilar materials. Complex cases sometimes might require the collection, examination and analysis of a large amount of evidences. These cases may involve multiple forensic experts having different backgrounds, commonly in biology, chemistry, physics, computer and other disciplines. These forensic scientists work independently to analyze the evidence in a particular case. For example, one forensic examiner might analyze latent print evidence, another compare glass pieces and third might be examining hair or carpet fibers using a microscope which was collected from the scene. The investigators will then combine all of the examiners' objective results to build a case report. 5. Scope of a Forensic Investigation The range of a forensics includes either one or all the three following major activities in analyzing and interpreting the physical evidences in the forensic science laboratories: I. Identification II. III. Individualization Reconstruction

8 I. Identification: The process of identification which is based on the class characteristics is common to all the basic sciences and, in fact, to all the items in everyday life. This system can also be used to classify the physical evidences, in which items having similar class characteristics are assigned to particular categories. The best example can be fibre, glass, hair or soil sample in which the class characteristics help in determining whether these samples are consistent with similar material recovered from a crime scene. Although fibers do not have any individualizing characteristics such as DNA, it does have class characteristics such as color, length, material and shape of the cross section etc. Comparison of class characteristics of fibre evidence with fibers recovered from suspects home, car, or clothing can help in the associating between the suspect and the crime scene but conclusive opinion can t be formed to determine the origin of fibres. Similarly in forensic science, the identification usually means the identification of items of physical evidence received in the laboratory, which demonstrate the possession of controlled substances to establish the element of crime. Some of the physical evidences required to conduct scientific tests to identify them. The sample of blood, semen accelerant and drugs required to be tested on the spot. Items are identified by comparing certain combination of class characteristics only with those of known standards or previously established criteria. Class characteristics are the common properties to all the members of a group or certain class of objects or substances produced in a single batch. II. Individualization: The forensic science has a responsibility to demonstrate that a particular sample belongs to whom. According to law of individuality everything in this universe is unique, even may be among members of the same class or any particular item manufactured in the same machine one after the other in a batch (Intra batch variations). It may also refer to demonstrate that a questioned piece of physical evidence and a similar known sample have a common origin or not.

9 Thus, in addition to class characteristics (characteristics which are common to a particular class/group of items or objects), objects and materials also possess certain individual characteristics (which are unique to a particular item) which make them unique and can be used to distinguish even among the members of the same class/group. The nature of these individual characteristics varies from one type of evidence to another, but forensic scientists have to take advantage of them in an effort to individualize a piece of physical evidence by comparison process. Only a few types of physical evidences like fingerprints, Hair, blood, broken small or bigger glass pieces, tool marks or markings present on bullet or other objects (primarily physical pattern evidence) direct physical comparison or physical matches (jigsaw fits) can be achieved, and can be called truly individualized. But with some other types of evidences, only partial individualizations are possible, and in some cases they are nothing more than refined identifications. The term identification is sometimes used to mean personal identification (the individualization of a person). Fingerprints, for example, can be used to "identify" an individual. The terminology is little confusing, but this process is really an individualization (linking to an individual). Likewise, forensic odontologists can make personal individualizations in situations (such as in mass disasters, or in cases of victims of arson or explosions) where dead bodies cannot be readily identified otherwise take the help of dental evidence and dental records. III. Reconstruction: Reconstruction is basically a final step of any criminal investigation. It refers to the process of putting together the "pieces" of a case or situation with the objective to reach an understanding of a sequence of past events. It can be achieved on the basis of physical evidence that has resulted from the events. Reconstructions are regularly desired in criminal cases in which eyewitness evidence is absent or unreliable. These are important in many other types of cases too, such as automobile accidents. Identification and individualization of physical evidence can play important roles in providing data for reconstructions in most of the cases.

10 By virtue of its nature, the forensic science has to do with legal matters and has close interaction with the criminal justice system. This feature and individualization sets it apart from traditional or basic sciences. Most of the forensic scientists are concerned almost exclusively with criminal cases, and they deal almost entirely with the criminal justice system. There are many kinds of civil cases too, however, in which physical evidence and Forensic Science have important roles to play. 6. Information the Physical Evidence Can Reveal Physical evidence may either be left behind by the perpetrator or some time picked up from the crime scene or victim. The evidences after their collection need to be analyzed, which is concerned with identification of traces of evidence, individualization and reconstruction of events. In every forensic science investigation, the aim of the evidence analysis is to provide useful information that can helps to make the facts of the case clear to the jury. Physical evidence analysis in general and their interpretation in particular can provide a number of the following different types of information related to crime: I. Information regarding the Corpus Delicti: The corpus delicti means the body of the crime refers to provide necessary information on the facts of the case to verify that a crime has taken place. It has often been interpreted that additional evidence are required beyond a confession to convict an individual for a crime. In other words corroborating evidence must be introduced before a confession may be admitted for trial. The example may be the ppresence of tool or track marks, blood stain, fingerprints, broken doors or windows, ransacked rooms and furniture, and missing valuables are all examples of corroborating physical evidences that would help in establishing a case of burglary. Similarly, in an assault case, the blood, a weapon, or torn clothing could be important physical evidence to prove in the court of law.

11 II. Information regarding the Modus Operandi: Modus operandi (MO) is a Latin term which mean method of operation and it refer to the manner in which a crime has been committed (Gross, 1924). A criminal s modus operandi is based on the choices and his behaviors that are intended to assist the criminals in the commission of a crime. Most of the criminals/ criminal gangs have a particular modus operandi, MO which is characteristic style/choices of using different weapons to commit a crime. Physical evidence can help in revealing these MOs. In arson cases, the type and the container used to carry accelerant and the way in which fires are set constitute MO. The physical evidence that helps to establish this pattern is called the MO or signature of an arsonist. Similarly in cases related to dacoity or burglary or terrorist strike has specific MO or signature of the criminal. Different cases treated separately can sometimes be connected by careful documentation of similar MO. Hence MO or signature of the criminal must be given sufficient weightage. III. Linking a Suspect with a Victim and weapon Linking a suspect with a victim and a weapon of offence is one of the most common and important particularly in violent crimes. This can be established by collecting and comparing the physical evidences from crime scene. Blood/ blood stain, hairs, blood present on the glass piece, clothing fibers, cosmetics and other such evidences may be transferred from a victim to a perpetrator. Items found in a suspect's possession can be linked to a victim, such as by comparison of cartridge cases or bullets or by analysis of blood found on a knife. It is also possible to trace the evidence may be transferred from a perpetrator to a victim. It become important that suspects and their clothing along with other belongings be thoroughly searched for trace evidences. The other belongings of victims should also be treated similar way.

12 IV. Placing a perpetrator at a Crime Scene Another linkage which is also a common and significant one is to establish by the analysis of physical-evidences the presence of perpetrator at the crime scene. Fingerprints and shoe prints, blood, body fluids like saliva and semen, hairs, fibers, soil, bullets, cartridge cases, tool marks, footprints or shoe prints, tire tracks, and objects that belonged to the criminal are some examples of deposited evidence. Depending on the type of crime, various kinds of evidence from the scene may be carried away. Stolen property is the most obvious example, but two way transfers (according to Locard s principle of exchange) of trace evidence can be used to link a suspect, a victim, or even a witness, to a crime scene. V. Supporting or Disproving a Witness's Testimony Physical-evidences are very powerful and reliable source of information related to crime activity at the crime scene. Analysis of different types of evidences can often indicate conclusively whether a person's version related to the set of events are believable or not. The best example of a driver whose vehicle matched with the description of a hit-and-run vehicle, an examination of the vehicle might reveal the presence of a blood on the bottom of the bumper. Now the driver explains the findings by claiming that his vehicle has hit a dog on the way. Tests on the blood for species identification can reveal whether the blood belongs to a dog or from a human. VI. Identification of a Suspect with DNA or other Individualizing Techniques The suspect/perpetrator can best be identified with the help of fingerprint evidence. A fingerprint found at a scene, and later identified as belonging to a particular person, results in an unequivocal identification of that person. The term identification as used here really means "individualization." Although people commonly say "identification of a suspect" or "identification of a fingerprint," this is not strictly correct. The distinction between the terms identification is based on class characteristics (i.e. identification of a particular group of items) and individualization is based on individual characteristics (i.e. identification of a particular item in a group).

13 VII. Providing an Investigative Lead Physical-evidence analysis can play an important role in directing an investigation along a productive path. In a hit-and-run case, for example, a chip of paint from the vehicle can be used to narrow down the number and kinds of different cars that may have been involved. A substantial part of the forensic analysis consists of making comparisons between questioned and known samples. Depending upon the degree of individuality exhibited by the samples, the following conclusions can be drawn about the association between the people and the physical evidence in different cases. When questioned and known samples are compared, the following three possible conclusions can be drawn: a. They match in all the properties used to compare them. In this case a common origin become possible (or with a few kinds of evidence where jigsaw physical fits or fingerprints, can be proven). b. They do not match. In this case, the possibility of common origin is excluded. Exclusions are unequivocal and provide unimpeachable evidence of non-association. Exclusionary findings can be most helpful in the conduct of investigations. c. In some cases, there is insufficient sample to make a conclusive comparison. In such an instance, class characteristics of the samples would be noted, but a conclusion could not be reached about the possibility of a common origin. Comparisons which demonstrate exclusions on the basis of physical analysis indicate that a prime suspect is innocent, that the investigation is not proceeding along a productive path, or initial theories about crime, what actually happened are wrong. In other cases, where comparison yields a match, the conclusions depend on the type of evidence involved. Fingerprints are uniquely individualizing if sufficiently detailed. Bullets and cartridge cases can mostly be unequivocally related to a particular weapon, provided if weapon is available for comparison.

14 Physical matches can provide proof of common origin with many types of evidence. Tracks and imprints can often be attributed to the object that made them. Therefore forensic science can be used an effective and powerful tool in the investigation of crime and prosecution of criminal if physical evidences are properly appreciated and utilized. 7. Summary 1) As each crime scene is unique and each case presents its own challenges, Complex cases may require the collection, examination of a large number of varied evidences. 2) The exact position/location of the evidences collected from the crime scene has been recorded. 3) The evidence can be helpful in linking the crime with the criminal on the basis of the results produced by the laboratory. 4) Linking a suspect with a victim and a weapon of offence is one of the most common and important particularly in violent crimes. 5) A substantial part of the forensic analysis consists of making comparisons between questioned and known samples.