What is forensic science?

 

Forensic science is the name given to the use of a range of sciences and scientific techniques to answer questions that are of interest to the legal system (see Figure 1).

 

Under the microscope

 

It is really important that scientists thoroughly investigate a crime scene and collect samples of any fibers, hairs, or bodily fluids that they find. These samples can then be analyzed in the laboratory and compared to any potential suspects (see Figure 2).

 

Fingerprints

 

See Figure 3.

 

Experiment with Ink Chromatography

 

Chromatography is the process of separating small amounts of substances from a mixture by the rate at which they travel through a medium. Ink is a mixture of colored dyes, so chromatography can be used to separate the mixture of dyes (see Figure 4).

 

Your task

 

Ask a friend to write a note using a black water-soluble pen and leave a dot as evidence on the bottom of some filter paper. Can you identify the pen that was used to write a note?

 

You will need

 

Several varieties of black water-soluble pens, including a sample of the evidence

Coffee filters cut into 2 cm wide strips

A ruler

A container

Some paper clips

Some water (solvent

 

What you need to do

 

Fill the container with 2 cm of water (solvent)

Use a 2cm wide strip of your evidence and hang it from the ruler (using a paperclip to secure). Allow the end of the paper to touch the solvent. However, do not let the ink get wet. Using a pencil clearly label the sample at the top.

For each of the suspect pens, place a spot of ink about 3 cm from the bottom of the filter paper strip. For the best results, allow the ink spot to dry and repeat. With a pencil clearly label each of the strips.

Secure each of the filter paper strips to the ruler with a paperclip. Ensure that the bottom of the paper just touches the surface of the solvent and that the ink spot does not get wet.

Allow the ink spots to separate for 15 minutes

Examine the patterns of each ink sample. Can you determine which of your known suspect pens is the pen used to write the note.

 

How does it work

 

When the ink sample comes into contact with certain solvents, the colored dyes dissolve and can be separated. By placing the filter paper with the ink sample into a solvent, the ink spreads across the paper when it is dissolved. The different colored dyes within the ink move at different rates along the filter paper.

 

Handwriting analysis

 

Forensic scientists can analyze handwriting so that written documents can be used as evidence (see Figure 5). Scientists can try to answer a number of questions, for example, who wrote it? When was it written? Perhaps scientists are analyzing a ransom note or a forgery.

 

Everyone has their own unique style of writing. So, even if a criminal tries their best to disguise their handwriting. It will still exhibit some of their characteristics. Forensic scientists are also interested in the type of writing instrument used. For example a quill and ink, a pen or a pencil. They also analyze the type of paper written on.

 

Cracking codes

 

Have a go: Cracking codes

 

The pig pen was first used in the sixteenth century. The cipher uses symbols to replace the letters in the message, as shown in the diagram below (see Figure 7).