Criminalistics 16-18

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Criminalistics 16-18

Who was Will West?

Will West, arrived at Fort Leavenworth prison. Aroutine check of the prison files startlingly revealed that a William West, already in the prison, could not be distinguished from the new prisoner by body measurements or even by photographs. In fact, the two men looked just like twins, and their measurements were practically the same. Subsequently, fingerprints of the pris-oners clearly distinguished them.

Under what circumstances have two people had the same fingerprints?

there are none to date.

It is estimated that there are as many as ________ ridge characteristics in an average fingerprint.

150 individual

The most commonly encountered ridge characteristics used by AFIS are what?

Bifurcation and ridge ending

Whats the minimum number of ridge characteristics necessary before two fingerprints can be identified as the same?

no minimum exists. final determination must be based on experience and knowledge from an expert.

The pores of the sweat glands are locared where?

The skin ridge

Prints that are not readily visable are commonly referred to as what?

Latent prints

Who attempted to destroy their fingerprints with corosive acid?

John Dillinger

The most common ridge pattern is what

Loops

Live scan images of fingerprints-know about how they work.

Have eliminated the need for inked prints on paper cards. Are sent to the AFIS database electronically. Do no need to be analyzed by people.

Ninhydrin is used on latent prints to detect what?

Protein material

In which order should chemical treatment to realize latent prints be performed?

1. Iodine fuming
2. Ninhydrin
3. Physical developer

After visualizing a latent print a investigator should do what next?

Take pictures

Which fingerprint pattern accounts for 5% of all patterns?

Arches

Which pattern has no delta?

arch

Which pattern has two deltas?

Loop

Which pattern has 3 deltas?

whorl

Recognize names of ridge characteristics.

a/k/a minutiae, Ridge endings, bifurcations, enclosures, and other ridge details, which must match in two fingerprints in order for their common origin to be established

Why are grooves rifled into the bore of a gun?

As a fired bullet travels through a barrel, it engages the rifling grooves; these grooves then guide the bullet through the barrel, giving it a rapid spin. This is done because a spinning bullet does not tumble end over end on leaving the barrel, but remains instead on a true and accurate course.

How is a shotgun barell differenct from a riffle barrel?

shotgun barell is smooth bored, and a riffle barell is riffled.

The comparison of two bullets is possible with the comparison microscope. Such an exam is made difficult by what?

The presence of grit and rust can alter the markings on bullets fired through the same barrel. recovered evidence bullets may become so mutilated and distorted on impact as to yield only a small area with intact markings. striation markings on a barrel are not permanent structures; they are subject to continuing change and alteration through wear as succeeding bullets traverse the length of the barrel.

Distinctive markings on shells and cartridges can be made by what?

metal- to- metal contact are caused by the extractor and ejector mechanism and the magazine or clip, as well as by imperfections on the fire chamber walls.

When a etching agent is applied the stamped area will desolve at _______ rate, as the unstamped area.

faster

When a gun is recovered from a underwater location it should be what?

dont dry or clean it. Instead, the firearm should be transported to the laboratory in a receptacle containing enough of the same water to keep it submerged.

Discharged bulletts must be carefully handled to avoid damage to what?

powder residues deposited around a bullet or shell hole.

Shoe & tire marks impressed into Earth can be best preserved how?

their preservation is best accomplished by photography and casting.

What firearm evidence would you not find marks or impressions on?

shotgun, because it has a smooth bore.

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