While these are just some of the questions to ask, if any suspicion of homicidal poisoning exists, investigators can do a number of things. For instance, detectives who suspect the suspicious death of a child can review the child's hospital records. The offender may be associated with the death of more than one child or person under his or her care. A thorough history of the caregiver's association with ill or deceased persons is essential in revealing a pattern of behavior. Remember to check records from more than one state. If the caregiver has access to transportation, he or she may take the victim to a number of hospitals or doctors in order to avoid suspicion. Some hospitals routinely flag patients who are examined at the hospital more than three times. Once a child is flagged, the medical staff will investigate the possibility of abuse.
The sudden death of an otherwise healthy adult also is cause for suspicion. Autopsies routinely screen for some toxins, but it should be determined in advance if the caregiver or spouse had access to unusual substances. This is particularly important if the persons with access to the victim can readily obtain uncommon medicines.
Pick your poison
Once the case goes to the forensic toxicologist, the real fun begins. There are literally thousands of poisonous possibilities. It is the job of the forensic toxicologist to narrow down the list of poisons that may have been used. This is done in several stages.
- Although unlikely, if the death scene is staged to look like a suicide, there might be needles and syringes, dishes or pill bottles as well as chemical containers present. These items should be tested to see if they yield any evidence of poisonous substances.
- The victim's urine can be tested for the presence of certain drugs. This is common in athletes and employment drug testing. However, some drugs will not be present in urine while others metabolize in the body into other substances. For example, forensic scientist Richard Saferstein notes that a toxicologist searching for the presence of heroin would be on a bit of a wild goose chase, since heroin rapidly metabolizes into morphine in the body. Substances that cause instant death may not be present in urine because the victim died so rapidly, the poison never reached the bladder.
- Blood and tissue in fairly small amounts can be used to screen samples in the hopes of paring the list of possible poisons, and then used in more specific tests to confirm the type of poison present. Many poisonous substances can be defined as either acids or bases. Using the pH scale of 1 to 14, with 1 being the most acidic, various substances can be added to water to determine how they affect the pH. Water is neutral at 7 on the scale. Adding an acidic substance to the water will push the acidic reading to between 1 and 7 on the scale. The opposite happens if a basic substance is tested. The scale reading will be in between 7 and 14.
In this way the toxicologist can determine what type of drug is present. For example, Saferstein points out barbiturates and aspirin are acidic drugs. Methadone, amphetamines and cocaine are bases. Some other poisons are tested for in the same way. These poisons include industrial products, pesticides and bio-toxins. Bio-toxins are very difficult to identify and come in several forms.
Once the general nature of the substance has been determined, several other tests can be used to confirm the exact nature of the substance. The most common tests for drugs are thin-layer chromatography, mass spectrometry and immunoassay, says Saferstein.
- Check the victim's hair and nails. Some poisons such as arsenic can cause specific growth patterns in the hair and nails of the victim. This only occurs if the poisoning takes place over a period of time as opposed to a single fatal dose. Chronic poisoning also may cause toxins to build up in the victim's hair follicles. The rates at which a toxin is stored differs between light-haired and dark-haired people. Dark-haired individuals seem to have higher levels of toxins in their hair follicles.
Poisoning is a unique type of crime. It is strangely "accepted" as less of a crime than a homicide involving physical violence. But this dastardly crime takes cunning and planning and causes its victims suffering beyond comprehension. Investigators must be ever-vigilant in their efforts to detect homicidal poisoning and bring its toxic perpetrators to justice.
Kathy Steck-Flynn, a member of the Canadian Society of Forensic Scientists, teaches seminars in forensic evidence and entomology. She writes the forensic science section for "Crime Watch Canada," where she is employed as a staff writer. She can be reached at firstname.lastname@example.org.