Forensic Science Lab Final

Calculations:

Density = mass / volume

Kilo, Hecto, Deca, Base, Deci, Centi, Mili

Understanding Chemical Compounds:

Methylene Blue = A dye that stains acidic animal cell components such as the nucleus, bacteria, and blood tissue for detailed observation.

Iodine = A solution that is used to stain cells and can be used in wet mounts.

DNA Charge and Composition:

• Key Concept: DNA has a negative charge due to its phosphate backbone.

Interactions with Chemical Compounds:

• Key Point: Methylene Blue is attracted to negatively charged molecules like DNA.

Microscopy Magnification Calculations:

• Formula: Total magnification = Eyepiece (ocular) magnification (10x) x Objective lens magnification

• Example Calculation: If the eyepiece is 10x and the objective lens is 4x, the total magnification would be 40x.

. Iodine Reactions with Biomolecules:

• Learn about iodine’s attraction to various biomolecules, especially those containing hydroxyl groups (OH).

• Examples: Iodine is attracted to starch, glycogen, and cellulose, which have multiple hydroxyl groups.

Extra (found in slides):

The source of energy that is used in microscopy is called electromagnetic energy

One of the most commonly used microscopes is called a compound light microscope

The stereomicroscope is one of the most frequently used microscopes when called upon to examine trace evidence obtained from a crime scene.

Pelvis analysis:

Females

Shaped like an oval; wider (to able to birth children)

Wider greater sciatic notch

Wide, curved pubic arch

Males

Shaped like a heart; narrow

Narrow, angular pubic arch

Narrow greater sciatic notch

Skull analysis:

Females

More pointed chin

Less pronounced mastoid process

Wider, less defined angle of a jawline

Males

More square chin

Pronounced mastoid process

An acute angle of a jawline

Extras (found on slides):

Most useful bone for determining sex = pelvis

Most useful bone(s) for determining height = long bones of arm or leg

Most useful bone for determining race = skull

Blood typing:

Blood group:

AB = universal recipient
O = universal donor

Antibodies present in blood:

Anti-B = binds to type B antigens

Anti-A = binds to type A antigens

Extras (found on slides):

  • A person with A antigens has anti-B antibodies

  • A person with B antigens has anti-A antibodies

  • A person with neither A nor B antigens has both anti-A and anti-B antibodies

  • A person with both A and B antigens has neither anti-A nor anti-B antibodies

Io= the intensity of light entering the solution

I  = the intensity of light transmitted or leaving the solution.

When human hairs do have a medulla, the medullary index for human hair is generally less than 1/3 (or 0.33)

Animal hairs most commonly have a medullary index greater than 1/2 (or 0.50)

Several types of medullae: continuous, interrupted, segmented, solid, or none

A continuous medulla has one unbroken line of medullary color down the middle of the hair shaft.

An interrupted medulla has a pigmented line broken at regular intervals where the visible areas of the medulla are larger than the areas where the medulla is not visible.

A segmented medulla has a pigmented line unevenly spaced.

A solid medulla has a pigmented area filling both the medulla and the cortex.

Other medulla, the ‘none’ medulla pattern, have no separate pigmentation in the medulla.

  • Ballistic imaging is a technique used to link a bullet to the specific gun from which it was fired. 

  • Bullet – the metal projectile that is propelled from the gun

  • Cartridge – a case that holds the bullet, primer, and gunpowder

  • Gunpowder – the source of energy to project the bullet

  • Primer – a shock sensitive material located at the base of the cartridge that ignites the gunpowder when struck by the firing pin

Fingerprint patterns fall into three basic categories: loops, arches, and whorls.

Loops: (1) radial loop, (2) ulnar loop

Arches: (3) plain arch, (4) tented arch

Whorls: (5) central pocket loop, (6) double loop, (7) plain whorl, (8) accidental

Each fingerprint is further made up of as many as 150 minutiae.

Plastic prints are found on soft three-dimensional surfaces such as paint, soap, wax, etc.

Patent fingerprints are visible without treatment.

Latent fingerprints are invisible until they have been discovered and collected using an alternate light source, superglue fuming, powders, or chemical developers.

Nonporous surfaces = smooth surfaces such as metal or glass.

Porous surfaces = materials that have small pores in them such as paper or cloth