X-Ray Diffraction (XRD) is a rapid technique used in forensic science to analyze crystalline material of various types of trace evidence, such as paint, drugs, and glass. The method identifies the crystal component of a sample (qualitative analysis) and also quantifies the amount of each element in a mixture (quantitative analysis). The principle of XRD techniques is that when the X-ray passes through the crystals, the x-ray beam is reflected out of the crystal’s plane. The beams mix with one another to form unique diffraction patterns which a chemist can use as ‘fingerprints’ for compounds of interest (Richard, 2011).
XRD analysis was initially used as a method of choice at the Institute of Criminalistics Prague (ICP) in the early 60s to identify short-circuits products on electric copper conductors. However, several modifications were made to this technique overtime to ensure that it is adaptable globally in different circumstances. Currently, X-ray diffraction method is applied in forensic science for many years. According to Rendle (2003), there are many advantages of XRD in forensic science. First, the technique allows analysis of tiny sample volumes. The methods allow analysis of samples as small as 0.000001 grams in weight. The use of the small sample is a significant strength of this technique primarily for forensic experts who usually work with small amounts of samples.
Delegate your assignment to our experts and they will do the rest.
Secondly, forensic experts may choose this method because it is relatively non-destructive. The samples used in this analysis can be used for further investigation even after crushing them to powder form. This characteristic allows for multiple analytical tests to be conducted in one sample naturally because most parts of the materials for analysis is always preserved despite the processing procedures.
The third reason why forensic chemists may consider this method is because it allows for the exact identification of phase s and components in a mixture. This is an invaluable feature of this technique compared to other commonly used methods such as the atomic absorption, emission spectroscopy, and neutron activation analysis. This technique has been used to determine explosives and residues collected blast scenes. Fourth, XRD analysis allows a forensic practitioner to quantify or semi-quantify substance in a mixture to approve a final report during court proceedings. For example, this method of study has been applied to identify unknown materials, poisons, and contaminants especially in cases of environmental pollution. Furthermore, in some cases, X-Ray Diffraction has been helpful in the analysis of narcotic mixtures, especially among drug traffickers. The technique is also commonly used in to identify and analyze pigments and paints for example during studies of abrasions, scratches, and fragments following motor vehicles accidents (Rendle, 2003).
Forensic application of X-Ray Diffraction is faced with a few significant challenges. First, only a few laboratories such as FBI laboratory in the United States (USA), BKA laboratory in Germany and a few other laboratories in Japan and Australia employ this technique. This feature means that the method may not be readily accessible to forensic experts globally. The slow adoption of X-ray diffraction methods by other laboratories may also be due to changes in diagnostics laboratories. Most laboratories are changing from manual interpretation methods to means of identification that use electronic databases (Rendle, 2003).
According to Richard (2011), a significant disadvantage of the XRD technique of forensic analysis is that the method is less sensitive. This feature means that the process can detect and identify the primary constituents of a compound but may not be able to identify those components which are less than five percent in a mixture. In this regard, a forensic chemist is usually forced to employ additional methods to identify elements of combinations which are minute to minimal in a mix.
References
Rendle, D. F. (2003). X-ray diffraction in forensic science. Rigaku J , 19 (2), 11-22.
Richard, S. (2011). Criminalistics: an introduction to forensic science .UK. Pearson Education.
