the application of the scientific method in forensic science

the Application of the scientific method in Forensic Science

Abstract

            The field of forensic science involves the application of the scientific method to questions related to criminal cases.  Forensic science follows the steps of the scientific method, from the observation of the crime science, collection of initial data, experimentation and validation of results that are generated from the analyses.  Molecular biology as well as other analytical techniques have been developed and improved the field of forensic science, resulting in precise details and additional information that could be used in court.

Introduction

The field of forensic science involves the application of the scientific method to questions regarding criminal cases (Brettell et al., 2007).  Similar to an experiment conducted by a scientist, a forensic science case allows a forensic scientist to use the four major steps of the scientific method in order to solve a criminal investigation.  To date, the results generated from forensic analysis are accepted as evidence in court hearings.  The power of forensic science was recognized as molecular techniques which were initially designed for biomedical purposes were applied to the judiciary system.  Methods in isolation, as well as manipulation, of deoxyribonucleic acid (DNA) from different types of tissues have facilitated the precise identification and comparison of biological materials between suspects and victims of a crime.  In addition, other assays involving other biological materials such as pollen and insects, have increased the specificity and reliability of the field of forensic science.

The analysis of insects, also known as entomology, has allowed a forensic scientist to determine stages of decomposition of human bodies, as well as determine whether a certain material of interest has been exposed or transported from one place to another.  On the other hand, the study of pollen or palynology, has facilitated forensic analysts in investigating conditions of the crime scene based on the presence and classification of pollen on the surfaces of materials of interest that were collected at the crime scene.  The employment of forensic data has thus revolutionized the field of criminal justice because it has provided an additional means of determining whether an individual should be convicted of a crime (Hunter, 2006).  In addition, forensic science has also helped in reviewing cold cases, or unresolved crime cases that are decades old, and has given light on the actual details of the crime.

A.      Observation and description of a phenomenon or a group of phenomena

Forensic science, similar to any scientific investigation, involves the observation and description of a phenomenon or a group of phenomena.  The usual phenomenon involved in a forensic case is a crime, wherein an unlawful act was performed in a specific area.  The location of the crime is known as the crime scene and it is important for a forensic scientist to look at the entire scenario in order to generate an initial assessment of the case.  The observation involved in this process includes the collection of photographs of the entire crime scene, as well as gathering smaller yet essential specimens such as blood stains, hair strands, fibers, pollen, finger- and footprints.

B.  Formulation of a hypothesis (or hypotheses) to explain the phenomena

Based on the initially collected information, the forensic scientist may generate a number of possible scenarios that could have taken place in the crime scene.  The possible scenarios formulated by a forensic scientist are equivalent to the hypotheses of a scientific experiment.  For example, the presence of blood in the crime scene easily signifies that there was some kind of physical injury that occurred at the crime scene.  However, it should be understood that with this kind of inquiry, there are several hypotheses that are presented.  One hypothesis is that some kind of physical assault was committed by an unidentified individual.  Another hypothesis could pinpoint a person of interest as a possible culprit of the crime.  A few other individuals can also be suspected to be involved in the crime.  However, it should be understood that unless a human body is found, it is difficult to determine whether a murder was indeed committed.  In addition to the question of who committed a certain crime, a forensic scientist also designs additional hypotheses which attempt to answer the question of how the crime was actually committed.  Formulation of hypotheses also includes the sequence of events of the entire crime, such as what the criminal first performed and when exactly was a certain murder committed.

C.  Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations

In order to answer the hypotheses that were formulated by a forensic scientist, all specimens collected in the site are brought into the forensic laboratory for further analysis (Lee and Ladd, 2001).  This step is thus equivalent to the experimental step of the scientific method.  The forensic analyses performed may include DNA profiling and fingerprint matches, as well as microscopic analysis of any fibers, pollens or microevidences that were collected in specific areas of the crime scene.  With regards to DNA profiling, a highly sensitive assay called the polymerase chain reaction (PCR) is employed to generate multiple copies of the DNA samples collected.  This assay allowed unlimited amounts of DNA from an individual that has been associated with the crime, including the victim and the suspects.  DNA profiling is important in identification because this is a fool-proof molecular method of matching specific DNA sequences of each individual.  These sequences are so unique that it is capable of distinguishing one individual from an entire human population.

Microscopy also allows that visualization of minute items that have been collected at the crime scene.  For example, small fibers are difficult to analyze using the naked eye or through magnifying lens and thus special microscope lenses can resolve smaller details such as the width and fiber details of clothes.  The gratings of bullets can also be viewed in finer detail using microscopes.  Forensic entomology is another technique that helps in forensic investigations.  The most frequently used insects are the maggots that usually appear in a dead body.  These larval-stage insects appear on decomposing bodies within hours after death and thus the collection of maggots from the crime scene can provide an estimate of the time of death of the victim (Vass et al., 2004).  These maggots can also provide information of the last meal that the victim consumed before his untimely murder.

D.     Performance of experimental tests of the predictions by several independent experimenters

Once the results of the forensic analyses are generated, these data are reviewed and validated by independent experiments.  This step is important because it determines whether the results reported by the forensic analysts are indeed reliable and correct.  The same conditions are also performed in scientific reports, wherein the results generated by one research group are replicated by at least one independent scientist in order to determine the validity and reliability of the research.  This step is also important because it is of utmost importance that the results that are generated from the forensic investigation are true because these can be used as evidence in a court trial.

The performance of experimental validation by independent experimenters also ensures that the information released by forensic analysts is indeed unbiased and true.  It should be understood that forensic cases are serious topics that are associated with the conviction or acquittal of a suspect, hence valid and reliable information must be generated from every forensic analysis.

References

Brettell, T.A., Butler, J.M. and Almirall, J.R.  (2007).  Forensic science.  Analytical Chemistry, 79, 4365-4384.

Hunter, P.  (2006).  All the evidence.  EMBO Reports, 7, 352-354.

Lee, H.C. and Ladd, C.  (2001).  Preservation and collection of biological evidence.  Croatian Medical Journal, 2, 225-228.

Vass, A.A., Smith, R.R., Thompson, C.V., Burnett, M.N., Wolf, D.A., Synstelien, J A., Dulgerian, N. and Eckenrode, B.A.  (2004).  Decompositional odor analysis database. Journal of Forensic Science, 49, 760-769.

 

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