In forensic toxicological analysis, various kinds of samples collected from crime scene or deceased are being analysed for the present of toxic substances or toxicant, including drugs. There are two key information that need to be included in the toxicology report, type of toxic substances presents its amount of concentration.

This information can be used to make inferences when determining a substances’ potential effect on individual’s death, illness, or mental or physical impairment. For example, the results of a blood analysis from a driver involved in a car accident can be used to determine if the individual was under the influence of drugs or alcohol.

According to Department of Chemistry Malaysia (JKM), toxicant can be of any substances that can bring harmful effects to the health of lived organisms when intentionally or unintentionally intake into body. Quantity or dose is the main indicator to differentiate a chemical substance of whether it is toxin or a therapeutic drug. Detection of drug and toxic substances in forensic samples are usually done by an initial screening and followed by a confirmation of the compounds. The screening and confirmation are usually, but not necessarily done with different analytical methods. The choice of method for testing is mostly depends on what kind of substance that toxicologist expects to find and the material on which the testing is performed. There are a variety of analytical techniques used in forensic toxicology laboratory, such as gas-liquid chromatography for examination of volatile organic compounds, atomic absorption chromatography for analysis of heavy metal, and high liquid performance chromatography (HPLC) for analysis of toxicant or poison.

In general, forensic toxicological analysis is a challenging field. Since most of the samples for toxicological analysis are biological samples, determination of the substance is often complicated as the substance had been through various mechanisms inside the body and is seldom remain in its original form. At the same time, the substance may also have been diluted by its dispersal through the body. The difficulty of analysis is further increased as the biological samples is more vulnerable to contamination.

In the context of fire investigation, accelerant can be referred as any substance or mixture that “accelerates” the development of fire. When accelerant is applied into a fire, more heat is produced, the reactant is consumed more quickly, and the spread of fire is increased as well. Fire accelerant plays a essential role in fire investigation as it provides valuable hint in determining the cause of fire. The accelerant used in arson cases can be presented in various form, such as liquid (gasoline or kerosene) and gases (propane or natural gas). In general, many accelerants are hydrocarbon-based fuels.

As in other investigation, the collection and packing of fire debris collected from fire scene must be carried out properly and carefully in order to avoid the destruction of evidence. Debris collected from a fire must be packed in tight, secure containers as the compounds to be analysed are often volatile. The packed sample is then sent to laboratory for further analysis.

There are multiple techniques in detecting the accelerants from the fire debris. The analysis of fire debris basically can be divided into two parts, extraction or isolation of volatile compounds which could be accelerants and identification of the volatile compounds which are completely isolated from the fire debris.

For the first part, there are few common methods which are being used in forensic laboratory, including solvent extraction, headspace extraction, and adsorption extraction. Once the isolation is completed, the volatile compounds are detected using a combined gas chromatography-mass spectrometry (GCMS).

Forensic analysis of accelerant is never an easy task. Recovery of fire debris containing accelerant at fire scene is a tough job as in most of the cases, the accelerant might be completely burnt off. Besides that, the fire debris also need to be handled properly as most of the accelerants are volatile. Correct analytical method must be chosen in order to obtain a good analysis result.

In a crime involving shooting activities of firearm, it is important for an investigator to determine who may have shot the firearm. In this circumstance, gunshot residue (GSR) is the most critical evidence in helping the investigator to reconstruct the crime. According to the Association of Firearms and Toolmark Examiners (AFTE), GSR is defined as the total residues resulting from the discharge of a firearm. It includes both gunpowder and primer residues, plus metallic residues from projectiles, fouling, etc. In general, gunshot residue can be found on the skin or clothing of the person who had fired the gun, on an entrance wound of a victim, or on other target materials at the scene.

Basically, the major primer elements are lead (Pb), barium (Ba), or antimony (Sb). In most of the cases, all the three elements are present. In forensic analysis, the major methods for detection of primer residues are analytical and qualitative. Analytical methods include atomic absorption spectrophotometry (AAS) and inductive coupled plasma-mass spectroscopy (ICP-MS), while qualitative methods include scanning electron microscopy with energy dispersive analysis (SEM-EDA) and atomic force microscopy (AFM).

The major problem with GSR analysis is the issue of possible contamination. There are many environmental sources of particles that can yield a GSR-like element and able to affect the analysis result when GSR is contaminated with these particles. Therefore, evaluation of GSR in the forensic laboratory need to be carried out in an extra careful manner in order to avoid the false positive analysis result. Besides that, GSR can also be removed easily from the surfaces they land on. Basically, regular activities such as putting hands in pockets and rubbing hands together can wipe them away. Thus, collection of GSR need to be carried out as soon as possible in order to prevent the loss of the evidence.

Although, there are a lot of limitations in GSR analysis, however, it still plays an important role in the forensic investigation as a useful tool in putting the pieces of the puzzle together, especially when GSR results are interpreted in conjunction with other evidences.