A toxicology screen is a test that determines the approximate amount and type of legal or illegal drugs that you’ve taken. It may be used to screen for drug abuse, to monitor a substance abuse problem, or to evaluate drug intoxication or overdose.

Blood and urine are commonly encountered, but oral fluid, hair, and other specimens are also used. Forensic toxicologists are frequently asked to determine the timing and extent of impairment resulting from different patterns of drug and alcohol use.

The field of forensic toxicology has grown to include drug and alcohol testing for employers and traffic enforcement officials as well as testing animal samples for wildlife criminal investigators and testing for “date rape” drugs and performance-enhancing substances.

“Four to six weeks is pretty standard,” Magnani says of the time line for forensic toxicology testing. Besides the time needed for painstaking analysis and confirmation, she says, there could be a backlog of tests that need to be done at a particular laboratory.

Hair: Hair is useful for drug use history and other toxicant or exposure determinations. Hair is also useful in cases of suspected chronic poisoning or remote acute poisoning that results in death.

Presumptive tests, such as those where a color change occurs, are those that usually identify a class of compounds whereas a confirmatory test, such as mass spectrometry, is one that conclusively identifies a specific, individual com- pound.

Cina says that autopsies are best if performed within 24 hours of death, before organs deteriorate, and ideally before embalming, which can interfere with toxicology and blood cultures.

These samples may include blood, fluid from the eye (vitreous humor), urine, bile from the gallbladder, stomach contents, and solid organs such as liver, brain, and lung.

The purpose of a presumptive test for blood is to determine whether or not it is likely that this body fluid is present; in other words, a positive result indicates the possibility of blood. A positive result of a confirmatory test for blood allows one to conclude that blood is present.

Luminol, leuchomalachite green, phenolphthalein, Hemastix, Hemident, and Bluestar are all used as presumptive tests for blood.

Phenolphthalein

Other common body fluids for which presumptive identification methods are routinely employed include blood and saliva. Such methods are typically based on the detection of hemoglobin (blood) through a phenolphthalein (Kastle-Meyer) test and the detection of saliva through an α-amylase test.

Since body fluids like semen, saliva, and vaginal fluids are naturally fluorescent, the use of a light source offers a unique method for locating them. The dried body fluids will actually glow under the light source illumination.

You see, blood does not fluoresce by applying UV or visible blue light. Although blood does not fluoresce, certain other physiological fluids will. UV alternate light sources can reveal the following: seminal fluid, saliva and urine stains.

Where Is DNA Contained in the Human Body? DNA is contained in blood, semen, skin cells, tissue, organs, muscle, brain cells, bone, teeth, hair, saliva, mucus, perspiration, fingernails, urine, feces, etc.

Gathering DNA Evidence DNA testing has expanded the types of useful biological evidence. All biological evidence found at crime scenes can be subjected to DNA testing. Samples such as feces and vomit can be tested, but may not be routinely accepted by laboratories for testing.

Unlike traditional DNA analysis, which can take weeks, Rapid DNA analysis processes DNA samples in less than two hours. This technology has the potential to change the paradigm for law enforcement.

Seven steps to understanding DNA fingerprinting:

1. Extracting the DNA from cells.
2. Cutting up the DNA using an enzyme.
3. Separating the DNA fragments on a gel.
4. Transferring the DNA onto paper.
5. Adding the radioactive probe.
6. Setting up the X-ray film.
7. Yes – we’ve got the result!

Unlike a conventional fingerprint that occurs only on the fingertips and can be altered by surgery, a DNA fingerprint is the same for every cell, tissue, and organ of a person. It cannot be altered by any known treatment.

DNA fingerprinting is extremely accurate….It can:

• Match tissues of organ donors with those of people who need transplants.
• Identify diseases that are passed down through your family.
• Help find cures for those diseases, called hereditary conditions.