Evidence and Investigation Review

Evidence - Recognize evidence of recent human activity, and recognize evidence of animal activity in a natural outdoor setting.

Footprints - Observe a set of footprints, and infer the direction and speed of travel

Analyzing Evidence - Recognize that evidence found at the scene of an activity may have unique characteristics that allow an investigator to make inferences about the participants and the nature of the activity, and give examples of how specific evidence may be used.

Evidence Sources - Investigate evidence and link it to a possible source; e.g., by:

i.    Classifying footprints,

ii.  Chromatography - analyzing the ink from different pens, using paper chromatography. 

iii. Writing samples - analyzing handwriting samples to identify a specific person

iv. Fabric - comparing samples of fabric

v.  Fingerprints - classifying fingerprints collected from a variety of surfaces.

Scientific Method

Hypothesis – an educated guess

Variables:

–Manipulated: What you change in the experiment

–Responding: What you are observing and recording

–Controlled: What you are keeping the same

Observations: WHAT YOU SEE.

Inference: Based on your observations, what you THINK happened.

●      You will be asked to look at pictures and determine inferences and observations

Circumstantial Evidence – Evidence that by itself can’t prove a person is guilty, because many people may have the same type of evidence, but can be used to support a case against a suspect. Example: A shoe print is circumstantial because many people could have the same kind of shoe. *Indirectly links a suspect to a crime

Conclusive Evidence – Evidence that directly connects a suspect to a crime. Proves beyond a shadow of a doubt that a suspect was involved in a crime. Example: DNA or fingerprint because no one has the identical DNA or fingerprints of another person. Although identical twins do have the same DNA.

Steps to solving a crime

1.     Secure the crime scene

2.     Prevent contamination

3.     Gather and document evidence

4.     Process the Evidence

5.     Gather Suspects

6.     Link Evidence to Suspects

7.     Conclusion

8.     Prove in Court

Footprints

•When looking at a set of footprints, investigators are able to determine how fast a person was walking or if they were running or jogging.

•When footprints are closer together, it can be concluded that the individual was  walking.

•Prints that are farther apart indicate that the person was running.

•Investigators can also tell how heavy a person was based on the depth of the depression left in the soil.

•Deeper tracks indicate a heavier person, while shallow tracks indicate a lighter person.

•They can also tell how tall a person is and what their shoe size is.

CHROMATOGRAPHY

•Investigators analyze ink on the note left at the scene of a crime to help figure out what kind of pen was used.

•Analyzing ink is done with chromatography.

•This is a method for analyzing complex mixtures by separating them into the chemicals from which they are made.

• Chromatography is also used to separate and identify all sorts of substances in investigative work.

•Permanent markers do not change

•Non permanent markers change in water

Steps for Chromatography

•Pour water into a cup

•Suspend note in water (not letting the ink touch the water)

•Remove note from water and let dry

•Compare note to samples collected from suspects

Graphology

• If a note or piece of a paper if found, investigators can analyze the writing.   They can also compare the handwriting on the note with samples from possible suspects

Steps

a)     the formation of the handwriting, such as the shapes of the letters (loop, dotted, crossed t) and their slant angles, connections and curves

b)    the line quality, or the thickness of the line as a result of the type of writing instrument used and the pressure exerted while writing

c)     the arrangement on the page, including spacing  or size of letters/words, alignment, formatting, how letters are joined and unique punctuation

d)    the content, including the spelling, phrasing, punctuation, grammar and style

Fibres

Natural Fibers- made from plant or animal (wool, cotton, silk, leather, linen and fur)

Synthetic Fibers- man made using petroleum products or other chemicals (polyester, nylon, rayon, and plastic)

●      Many tests can be carried out on fibres. The easiest one to do at a crime scene without touching the fibre is the colour test.

Finger Prints

•Whorl- Circles that do not exit on either side of the print

•Arch-  lines that start on one side, rise into hills and then exit on the other side of the print

•Loop-  lines that rise up and exit on the same side of the print

•Composite - combo of the above or something that does not fit the others (not used by detectives anymore, would be classed as a whorl)

Fingerprints are unique to each person not even identical twins have the same Fingerprints!

DNA

•DNA is called deoxyribonucleic acid and is found in physical evidence such as:

-       White blood cells

-       Saliva

-       Hair with the root

• Each person’s DNA is specific to them and only them (identical twins have the same DNA)

•DNA can prove opportunity placing someone at the scene of a crime