Forensic science is one of the accurate methods of collecting and analyzing evidence from a scene of a crime. Since courts require substantial evidence, investigators ought to use the most accurate forensic equipments and to follow all the necessary steps. Investigators use different approaches to collect biological evidence at the scene of a crime.
Chisum and Turvey posit, “All biological evidence is subject to deterioration and requires a lot of care” (2000, p. 23). Investigators may collect a number of biological evidence ranging from blood, hair, seminal fluid, to bones and organs. In case the investigators collect blood sample as their evidence, they do it using two five-milliliter tubes. Saferstein alleges, “The blood should be collected in vacutainers with Ethylenediaminetetraacetic acid (EDTA) as anti coagulant” (2000, p. 45).
On the other hand, if researchers are to collect a blood sample from a postmortem subject, they ought to “get it from the non-body cavity areas such as heart or chief internal blood vessels” (Saferstein, 2000, p. 46). For easy identification, researchers need to label all blood samples accordingly.
In case the researchers wish to collect liquid semen as their evidence, they use disposable pipettes or clean syringes to put it into disinfected tubes. Otherwise, they may use cotton wool to collect the liquid semen. They can use the cotton wool to absorb the semen, air-dry the content, and utilize it in forensic investigations.
In many cases, scientists use swabs to collect trace samples (Chisum & Turvey, 2000). The target area is rubbed severally using a moistened swab to collect biological traces. Nonetheless, moist swab may fail to collect adequate traces, therefore, calling for multiple swabs. Today, investigators use double swabbing technique to collect adequate traces.
After collecting traces from the crime scene, they are taken to laboratory for analysis. Analysts look for a number of clues that may help to identify the criminal. For instance, when analyzing blood sample, analysts look for the presence of genetic markers, which resemble those of the prime suspect.
If a crime involves beating or stabbing, chances of exchange of blood between the perpetrator and the casualty are high (Chisum & Turvey, 2000). Hence, analysts try to determine if the blood sample contains genetic markers that would help them identify the perpetrator. To substantiate a rape case, researchers look for traces of semen in the victim.
In the absence of semen, they look for traces of pre-ejaculation fluid. Investigators conduct a DeoxyriboNucleic Acid (DNA) test on the semen or pre-ejaculation fluid obtained from the victim and the results compared to those of the suspect. This helps to arrest the criminal involved in the crime (Houde, 1998).
Forensic evidence presented in court influences the judgment an attorney makes. Therefore, to make sure that the parties involved receive justice, forensic researchers need to be accurate in collecting and analyzing their evidence. One of the ways through which investigators may enhance accuracy of the results is by ensuring that they use disposable instruments to collect biological traces. Disposable instruments would minimize chances of contamination (Houde, 1998).
In addition, investigators ought to air-dry the collected fluid before packing to avoid chances of it reacting with the packaging material. One of the reasons why investigators fail to obtain accurate results is that, their biological traces contaminate the evidence (Houde, 1998).
To control this, investigators should make sure that they wear gloves to prevent the likelihood of touching the biological traces they intend to collect. Other mistakes that investigators need to avoid include, coughing, sneezing, or talking over the evidence. Coughing, sneezing or talking over the evidence might alter the results if the traces are exposed to investigators’ saliva (Houde, 1998).
Crime scene researchers may be asked to defend their findings in a court of law. In such a case, they would have to prove that their research observed all the necessary procedures. They would have to prove that investigations followed the outlined chain of custody (Kelly & Wearne, 1998).
The chain of custody starts after discovering the evidence and accounts for individuals that realized and gathered the evidence. Besides, it accounts for the method used to collect the evidence and the duration that every activity took. Investigators are advised to take photographs of the scene of crime before collecting evidence. The photographs help to, “identify where the evidence was located inside the scene of crime and its relation to other paraphernalia found at the scene” (Kelly & Wearne, 1998, p. 72).
Hence, researchers may include photographs to reinforce their evidence. Additionally, investigators would have to convince a judge that they followed all the guidelines when collecting biological traces. Presence of an expert witness would help the researchers in defending the integrity of their evidence.
Chisum, W. & Turvey, B. (2000). Evidence Dynamics: Locard’s Exchange Principle & Crime Reconstruction. Journal of Behavioral Profiling, 1(1), 22-37.
Houde, J. (1998). Crime Lab: A guide for Nonscientists. Rolling Bay: Calico Press.
Kelly, J. & Wearne, P. (1998). Tainting Evidence: Inside the Scandals at the FBI Crime Lab. New York: Free Press.
Saferstein, R. (2000). Criminalistics: An Introduction to Forensic Science. New York: Prentice-Hall.