The scientific method applied to criminal forensics investigations

Criminal Science

Applying the Scientific Method in the Real World: From Observation to Experimentation in Criminal Forensics

The scientific method is a very useful methodology for coming to objective conclusions about certain phenomena based on empirical evidence. Essentially, this method is utilized to discover the truth about a situation or event by first observing something, formulating a hypothesis that explains the observation, using the hypothesis to make certain predictions about other causes and effects, and conducting an experiment to test the hypothesis and the various subsequent predictions. This method is employed in many fields, and not all of them are traditionally though of a "science" by the masses. The area of criminal justice, for instance -- and especially forensics -- depends heavily upon the scientific method in order to generate valid and trustworthy results to be used in the solving of crime.

Observation

The observational stage in a scientific forensic pursuit often consists of the meticulous gathering of information -- this is not a field where any observation can serve as an area for study and experimentation, but rather the forensic scientist make sure to observe all possible fact regarding a crime scene and/or case before developing both partial and comprehensive hypotheses (Shodor 2009). This is somewhat different than in many other applications of the scientific method, where a given set of observations is purposefully studied to the exclusion of all else; the observations in forensics must all be accounted for.

One very simple example of this shows how much work is involved -- and how much the rest of the forensic undertaking depends upon -- the observational step in the scientific method. Imagine that a murder has taken place in a bathroom -- a place that is notorious for its remnants of biological material, including various fluids, hairs, and other substances. The majority of these will end up having no veering on the case, most likely, but rather will have accumulated during the normal course of use of the bathroom. In order to develop an effective hypothesis of the crime, however, it is necessary for the forensic scientist to gather all possible evidence during the observation step. There will most likely be some biological clues left by the murderer, and these cannot be distinguished at this stage.

Prediction

After the first round of hypotheses is made, they can be used to make predictions concerning other observations and even unobserved events and data points. The accuracy of these predictions, obviously, depends upon the quality of the hypotheses, which in turn depends on the level of detail and care taken during the observational phase of the scientific method. At the same time, there is a different element introduced in the pursuit of forensic science that is not dealt with in other branches of scientific inquiry. As the question of justice is also central to any forensic proceeding, the suspect's account of events and/or hypothesized explanations for observations must also be taken account (Young 2009). In this way, both verification and falsification can be used during experimentation.

Before these experiments take place, however, the predictions must lay out a way to clearly identify the expectations of the experiments, as well as a way the methods by which they should be conducted. Several predictions can usually be made rather quickly after the hypothesis that are fully testable and easily determined. Based on hairs found at the crime scene, for instance, it could be predicted that skin found under the victim's fingernails was of the same DNA as the on-matching hairs found on the bathroom floor. Based on the injuries that led to the victim's death, predictions as to the method of death and the size and shape of the weapon (if any) can also be made. All of these things can be tested for based on physical and empirical fact, but only after a solid prediction has been made. Without these predictions, there would be nothing for the forensic scientist to test.

Experimentation

This final step in the scientific method determines exactly how accurate and valid the other steps were in describing the physical events of the crime. Even with very careful observation and rational hypotheses and predictions, however, experiments can show that the assumptions of the forensic scientist were incorrect. This is why it is important not only for the lead forensic specialist to conduct falsifying (or verifying) experiments, but also to have other independent tests performed, to ensure that previously made predictions do not color the results of the experiments. This is one of the most often overlooked elements of the scientific method, even and perhaps especially in forensics (Vogt 2009).

In the hypothetical example used above, several experiments present themselves. When it comes to identifying the hair samples and/or matching them with skin cells found under the victim's fingernails, there are several types of DNA testing that can yield valuable and court-admissible results. Likewise, following predictions as to the size and shape of a weapon, experiments can be conducted that attempt to match various instruments to the wound -- the prediction narrows down what is being looked for, possibly even to a single item, and if that item or items is found to match the wound, the experiment may have successfully identified the murder weapon. It is still highly important at this stage to refrain from absolute certainty on the part of the forensic scientist; this goes against the principles of science and of the justice system. Independently confirmed experimental results, however, can show beyond a reasonable doubt what the likely events and circumstances of a crime were, making the objectivity and independent nature of this last step of the scientific method especially important in forensics.

Conclusion

The scientific method is not always enough to lead to a conviction in criminal cases. Without its application in forensic endeavors, however, our justice system would be based far less on fact and more on conjecture -- it would, in essence, be less just. It is the objectivity of the scientific method that enables the justice system to operate fairly and with greater impunity and authority.