Discussion Question: Luminol is a powerful tool for finding trace evidence, and may give investigators the chance to solve an otherwise cold case. They are several other forensics techniques that can crack a cold case and lead to closure for a victim or a family.

So, how should we balance police resources toward forensic departments with these capabilities verses patrol etc to maximize the efficiency of the crime stopping force?

Consider:

Should we use criteria to determine whether a case gets attention or the department gets the funds for cases.

If forensics has new equipment they stand a better chance of closing the case.

If a department is understaffed they can’t process all of the evidence.

If a case can be solved quickly with solid forensics evidence then investigative man hours may be saved.

More officers on the street may catch more criminals, discourage crime by their presence and make citizens feel safer.

My solution is large centralized forensics departments that are fully funded and well staffed in larger cities that need the lab.

Outlining departments give a flat amount of their budget to be a “member” of this lab.

If they need forensics work done, they send it to the lab for a fee.

Benefits: Distributes the cost of a forensics lab around the region; smaller departments can’t afford to maintain a big lab.

Cheaper than a private lab.

Good funding ensures new equipment.

Good staffing gives a chance for speedy processing.

Leaves funds for other police assets.

Introduction:

Evidence is easy to find when there’s blood everywhere, but what about when things have been cleaned up?

If blood evidence is suspected in the area, Luminol can be sprayed to detect it.

Luminol is a chemical compound that glows green-blue when it comes in contact with blood or other fluid stains.

The green-blue glow is called chemiluminescence.

In 1937 Walter Specht at the University Institute for Legal Medicine in Jena, Germany developed Luminol as a test for blood.

The test is so sensitive that it can detect blood in the parts per million range – even if it’s years old!

So, if there were one drop of blood in 999,999 drop of water, the luminal reagent glows!

Practical Uses

Luminol is used if there is no obvious evidence in the area and a violent or sexual crime is suspected.

Investigators darken the room. Luminol is sprayed over a wide area where the criminal actions are suspected to have occurred.

If there is blood or other fluid in the area, Luminol will glow green-blue.

Glow time is important because different fluids glow for different periods of time and at different intensities.

How Luminol works Chemically

The chemical name for Luminol is o-aminophthalyl hydrazide.

Luminol crystals are mixed up in water (called an aqueous solution) which has a pH of 10.5 - that’s called basic. Normal water is pH 7 neutral.

Hydrogen peroxide is added to the basic solution and the reaction mixture is set.

Luminol and hydrogen peroxide react in the presence of base very slowly to give light, but there’s not enough light to see because the reaction goes too slow.

A catalyst speeds up a chemical reaction, so that’s what we need to get lots of light so we can see it. - The catalyst is the iron in human blood.

Examples of how Luminol can help a cold investigation:

Trace amounts of blood detected on a carpet can indicate a pool of blood under the carpet.

Luminol may uncover the spray pattern from a gun shot wound (spray analysis is used to determine the angle)

How a body was dragged.

Bloody foot prints may be detected and can link a suspect.

If blood evidence is detected, it is video taped and photographed with special techniques to show the chemiluminescence and evidence is collected.

Drawbacks:

A big drawback to Luminol is that it detects through a chemical reaction with blood and thus destroys evidence.

Other compounds (including BLEACH and metal) react with Luminol so it is not a surefire test for blood. Further tests are always needed.

The glow of metals fades quickly, while the glow of blood fades slowly. Experts can tell whether they might have blood on their hands when using Luminol based on glow time.

Safety recommendations around chemicals and blood:

Luminol irritates the eyes, skin and lungs.

Blood can be contaminated with diseases.

Wear gloves, eye protection and a surgical gown to protect against these dangers.

Decontaminate yourself and your gear when you’re done with dilute bleach.

Sources:

http://ptcl.chem.ox.ac.uk/MSDS/AM/5-amino-2,3-dihydro-1,4-phthalazinedione.html

http://www.forensicdna.com/Timeline020702.pdf

http://dsc.discovery.com/fansites/onthecase/toolbox/tool_01.html#

http://www.crimelibrary.com/criminal_mind/forensics/serology/3.html?sect=21

http://people.howstuffworks.com/luminol2.htm