Grade 6 Science

Subtitle

Evidence & Investigation

A crime has been committed.  Can you catch the crook?

Fingerprints

Fingerprint Categories

Arch patterns have ridges that start on one side of the print, rise toward the center, and leave on the OTHER side of the print.  Arches have NO deltas (triangular pattern).

Loop patterns have ridges that start on one side of the print, rise toward the center, and leave one the SAME side from which they started.  Loops have ONE delta.

Whorl pattern ridges make lots of circles that DO NOT leave either side of the print.  Whorls have TWO deltas.

Composite patterns are a combination of two or more of the other three types of patterns. 

Composite pattern.

Delta - a triangular shape found in many prints.  See above.

Ridge Characteristics

Ridge Ending - A ridge ends.


Lake (Enclosure on the diagram) - A ridge in the shape of a circle/ oval.


Bifurcation (fork) - One ridge splits to form two ridges.


Island - A very short ridge in the print pattern is not connected to any other ridge, much like an island floating by itself.





Image credit: https://goo.gl/zgEgTf

Lifting Latent Prints

A latent print is a print which is left on a surface and cannot easily be seen.  The procedure for lifting latent prints is:


  1. Rub your fingertips on your face or scalp to ensure they have some oil on them.
  2. Roll your finger left to right leaving a print on the surface.
  3. Lightly brush white powder (corn starch, flour, baking powder, talc) over the print.  Use very little powder.
  4. Carefully blow the excess powder off the print. The print should now be visible.
  5. Use clear tape to lift the print by pressing the tape gently onto the print and lifting it..
  6. Place the tape on black paper to show the print clearly.

Chromatography


Question: Is black ink really black ink?


Chromatography is a technique used for separating mixtures.  We use a solvent (water) to separate different pigments which have been mixed to form black ink.

Key Terms - Definitions, and Topic

Capillary Action: The tendency of a liquid to be drawn upward. (chromatography)

Cast: A molded mass of plaster. (footprints and tire prints)

Chromatography: Separation of a mixture into its component parts. (chromatography)

Controlled variable: A variable which is kept constant and unchanging.

Evidence:  The facts available for proving or supporting a notion.

Forensic:  Of or used in a court of law.

Graphology: The study of handwriting. (graphology)

Hypothesis: A proposition or supposition made from know facts as the basis of an investigation: a "best guess" as to what will happen.

Interlocking weave: Fabric knitted with closely-interlocking stitches. (fabric analysis)

Investigation: A careful study of something in order to discover the facts about it.

Latent: Concealed; not clearly visible. (fingerprinting).

Litmus paper: A blue-coloured paper stained with litmus (made from lichen), that is turned red by an acidic substance, and restored to blue by an alkaline substance; a pH indicator. (soil analysis)

Manipulated variable: A variable which is changed to affect the results of an experiment.

Mnemonic: Designed to aid the memory.

Pigment: A substance that imparts colour to other materials. (chromatography)

Porosity: The degree to which an article is able to be permeated by water or air.

Prediction: A foretelling of what might be expected.

Responding variable: A variable which changes in response to another variable being manipulated.

Scenario: An imagined sequence of events.

Solvent: A substance (usually a liquid) that can dissolve other substances. (chromatography)

Synthetic: Human-made. (fabric analysis)

"Mr. Kerr, What Will We Be Learning in our Evidence & Investigation Unit?"

Understandings - Topic D: Evidence & Investigation

Students sharpen their skills in observing and interpreting what they see by investigating evidence of human and animal activity. They explore and analyze indoor and outdoor environments as they look for footprints, markings, evidence of disturbance and things that are left behind. Through these studies, students learn to pose questions, devise investigations, recognize patterns and discrepancies, and think logically about what they have observed.


General Learner Expectations

Students will:


6-8 Apply observation and inference skills to recognize and interpret patterns and to distinguish a specific pattern from a group of similar patterns.  

6-9 Apply knowledge of the properties and interactions of materials to the investigation and identification of a material sample.  


Specific Learner Expectations

Students will:

  1. Recognize evidence of recent human activity, and recognize evidence of animal activity in a natural outdoor setting.
  2. Observe a set of footprints, and infer the direction and speed of travel.
  3. 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.
  4. Investigate evidence and link it to a possible source; e.g., by:
    • classifying footprints, tire prints and soil samples from a variety of locations
    • analyzing the ink from different pens, using paper chromatography
    • analyzing handwriting samples to identify the handwriting of a specific person
    • comparing samples of fabric
    • classifying fingerprints collected from a variety of surfaces.