Crime Scene Exam 3

Non-expert witnesses must state only:

Facts. (Not opinions.)

An expert witness is a person who:

Is skilled in a specific occupation or trade and, because of this skill/knowledge, is qualified to analyze or compare a stated set of facts and render an opinion based upon those facts.

Qualifications of an expert witness.

Education, training, licensing, board certification, specific experience in their area of expertise.

To be able to testify in court, the expert must be:

Qualified by either prosecution or defense counsel

To establish credibility of an expert witness, the counsel needs to establish:

Whether they are formally educated or self-taught; their actual practical work experience; prior court testimony experience; the extent of specialized training required for their field.

Perforation

Bullet passes through and exits.

Penetration

Bullet enters but does not exit.

contact wound

muzzle of weapon is in contact with the tissue or the clothing covering the tissue

Near contact

The muzzle being held at a distance that results in “powder tattooing”

Intermediate range

Between 5 and 40 inches from the wound.

Characteristics of a contact wound

Edges of the wound are seared by hot gases from the gun; there is soot embedded in surrounding skin/fabric.

There generally will not be gun powder particles visible because they enter the wound.

Distance wound

Lack of soot, searing, or powder

Three types of trajectory analysis

Internal ballistics

External ballistics

Terminal ballistics

Ricochet

A projectile making glancing contact with a surface and continuing flight.

Internal ballistics

The processes involved inside the gun as the bullet is fired and travels down the barrel. (Conducted by a forensic firearms examiner.)

External ballistics

The events that occur after the bullet leaves the barrel of the gun but before it strikes its target. (Conducted by the crime scene analyst, possibly firearms examiner.)

Terminal ballistics

Defining the path of a bullet through the

body, the associated damage and differentiating

entry from exit wounds. (Conducted by a forensic pathologist.)

Deflection

A deviation in the projectile's normal path through the atmosphere as a consequence of an impact with some object.

Rifling characteristics

Lands and grooves on the surface of a projectile created by traveling through the gun barrel.

Range determination

Using the weapon and similar ammunition to create gun powder residue standards at different distances, then comparing to the questioned residue.

Items in a trajectory kit

Trajectory rods, centering guides, angle finders, lasers (sometimes)

Trajectory

A fired bullet's path.

Most accurate way to determine bullet trajectory over a short distance.

Connect two impact locations separated by sufficient distance via laser or trajectory rod.

How to recover fired components

Cut into walls (being careful of electrical wire and pipes)

Cut off a piece of fabric (Cut three sides

of a square a sufficient distance away from

the hole and then fold the fabric back.)

Cut into a solid structure (Cut

irregular shapes and mark a direction.)