Advanced Crime Scene Processing Exam 2

What are the purposes of BPA?

Direction blood drop was traveling

angle of impact on a surface

area drop originated

nature/type of force

direction of force

nature of object use

minimum number of blows

relative position of people and items involved

possible sequencing.

What are the limitations of BPA?

It has a lot of room for error based on angle and the math involved.

What information can be provided during crime scene reconstruction with BPA?

Where suspect was standing

Minimum number of blows

Placement of victim

Voids where items may have been moved

Why is it important to avoid conclusions with absolute cetainty?

BPA includes a lot of margin for error in selecting stains, separating patterns, and overall subjectiveness.

What effect does the target surface on bloodstain size, shape, and appearance?

Smooth surfaces allow for more usable stains while rough surfaces cause distortion.

What is the relationship between the shape of a stain and the angle of impact?

The more elliptical the stain, the smaller the angle of impact.

How do you determine the directionality of a bloodstain?

The tail of the bloodstain will point in the direction of travel.

What is point of convergence?

The point of convergence is the area where multiple bloodstain patterns meet to show the area of origin.

What is area of origin?

The point where all of the patterns radiate out from and combine (similar to Point of Convergence)

What are the 4 major categories of bloodstains?

Passive

Transfer

Impact/projected

Miscellaneous

What is a passive bloodstain?

Bloodstains which are the result of normal gravitational flow

What are examples of a passive bloodstain?

Pools

Flows

Drips

Clots

What is a transfer bloodstain?

Blood that is deposited through contact transfer

What are examples of transfer stains?

Pattern transfer

Swipe

Wipe

Smear

What is a pattern transfer?

When blood is transferred in the shape of the object it is on.

What is a wipe stain?

When blood is on a surface and it is disturbed

What is a swipe stain?

When blood is on a person and the move across a wall.

What is a projected/impact bloodstain?

Blood dispersed from a point/area source by a force

What are examples of Projected/Impact stains?

Arterial

Cast-off

Spatter

Expiratory

Splash

Spine

What is expiratory blood?

Blood that is mixed with saliva expelled from the airways

What are arterial stains?

Blood ejected in volume with heart beats

What are cast-off stains?

Bloodstain patterns that are coming from the weapon used when rearing back

What constitutes a miscellaneous bloodstain?

Any bloodstain that does not fit into the other four categories

What are examples of miscellaneous bloodstains?

Fly Spots

Skeletonized stains

Void/ghosting

What are the major and minor axis of an elliptical bloodstain?

The major axis is the longer length of the stain and the minor axis is the smaller length

How does a stain shape change with angle of impact?

It becomes more elliptical the smaller the angle of impact

How can direction of travel be determined from stain morphology?

The direction of the tail is the direction of the travel

What is the formula used to calculate angle of impact?

$$\theta=\sin^{-1}\left(\frac{wid\operatorname{th}}{leng\operatorname{th}}\right)$$

What is the characteristic of a stain approaching a 90 degree angle?

Circular

What is the purpose of overall, mid-range, and close-up photography of blood stains?

Overall shows the overall area

Mid-range establishes the placement of the pattern

Close-ups allow the patterns to be fully seen and examined

What are the procedures for overall, mid-range, and close up photographs of blood stains?

Overall taken first

Mid-range taken next with obvious landmarks

Close-ups should be taken with and without scales on both the whole pattern and individual well-formed stains. Macro photos are also necessary.

What is the purpose for roadmapping in BPA?

Allows determination of type of stain and separates patterns

What are the procedures for roadmapping in BPA?

Label each pattern of interest

Label individual stains within the pattern

Add reference scales outlining the patterns

What is the purpose for pattern and individual stain labeling?

To help keep the patterns and stains organized

What are the procedures for pattern and individual stain labeling?

Label each pattern

Identify 4 main stains in each pattern

Place a labeled scale next to each stain

What is the purpose of proper scale placement?

It allows for proper measurement.

What are the procedures for proper scale placement?

Length of scale must be parallel with the major axis

What is the purpose of selecting well-formed stains for analysis?

Helps establish parameters under which the stain, and pattern overall, was created.

What are the procedures for picking a well-formed stain for analysis?

A well-formed stain is one that is divided along it’s axis the opposite sides are approximately equal.

What are the measurements needed for analysis?

The minor and major axis of the stain.

Which stains have the greatest potential evidentiary value?

Well-formed stains

What is the prioritization of stains for DNA collection?

Least to most invasive, collect the ones you can without destroying episode

What is representative sampling?

Collecting samples from each pattern of importance

What is a penetrating bullet defect?

Projectile enters but does not exit

What is a perforating bullet defect?

Projectile enters a surface and then exits

What is a ricochet?

Projectile deflects off a surface

What is the difference between frangible and non-frangible surfaces?

A frangible surface crumbles and non-frangible surface that tends to stretch.

Why will one projectile create multiple defects?

Any ricochet or perforation

What are the limitations of using defect dimensions to infer projectile caliber?

Defects in some surfaces may be smaller or larger than the caliber of the bullet

What should be documented before use of trajectory rods?

Dimensions

Height from ground

Distance from nearest corner

Why is size of the defect important?

To help in angle determination

Why is the location of a defect important?

Can lead to approximate location of the shooter and helps to place the altercation

Why is the height of a defect important?

Helps to place the location of the shooter

What is the purpose of a trajectory rod?

Help to determine angle of the shot

What is the appropriate placement of a trajectory rod?

Directly in the center through both entry and exit

In what ways should you use a protractor?

Can measure both vertical and horizontal angles

Which directions should you get trajectory angles from?

Vertical and horizontal

What are some of the additional supplies used during trajectory reconstrution?

Angle gauges, plumb bobs, o rings, lasers

What information is used to estimate the probable location of a shooter?

The angle of trajectory and entry and exit defects.

What limitations are there in determining an exact shooter position?

Angles can be wrong and penetrating angles can hurt the estimation

What is the relationship between gunshots, projectiles, defects, and cartridge cases?

They all can lead to helping place the location of the shooter.

What is a radial facture?

Fracturing of glass in a circle then branching out from the defect

How can you sequence shots in glass?

The intersections of radial fractures, the ones of the second shot will terminate at the fractures from the first

How is tempered glass effected by gunshots?

Tempered glass fractures into a mosaic pattern with no sharp edges

What is the 3R Rule?

Lines on Radial fracture edges form a Right angle on the Reverse side of the force

How can the 3R Rule be used to determine direction of force?

The fractures right angle goes opposite the direction of force

What is the visibility and lighting issues in water scenes?

Objects are distorted and only blue and green wavelengths are let through

How can evidence be lost or moved in underwater recovery?

Water shifts it and if the body of water is large it would be impossible to find and pin point.

What is done for diver safety during underwater recovery?

There are multiple divers and people on land are suited up ready to go if something happens

How should evidence be recovered and packaged?

In the water in water tight packages

What are the 5 search approaches for underwater scenes?

Circle

Arc/pendulum

Jackstay

Snag-line

Compass

What is a circle search?

Circumference of a circle around a fixed point at various distances

When should a circle search be used?

Big spaces

What is an arc/pendulum search?

Searcher moves back and forth in a pendulum fashion to one side of fixed point

When should you use an arc/pendulum search?

Big area with a wall or bank

What is a jackstay search?

Two searchers move in opposite directions from fixed jackstays along a moveable jackstay

When should you use a jackstay search?

When the area is large and cannot be covered in a circle

What is a snag-line search?

Weighted lines can be used to “snag” the target to speed up the search

What is a compass search?

An underwater compass is used for directionality and “kick cycles” for distance

What is the basic search team composition for underwater scenes?

Team Leader

Line Tenders

2 Divers, primary and safety

What is the role of a team lead?

Supervises the diving process

What is the role of a line tender?

Tends the line while divers search

What is the role of a safety diver?

Be a back up for the primary diver and ensure the safety of the team

What is the role of a primary diver?

To dive for the evidence and collect and mark any evidence found

What is the type of evidence commonly targeted during underwater searches?

Bodies, vehicles, and other evidence of crimes

What are the considerations necessary for recovering bodies and physical evidence?

It must be bagged in the water before it is removed

What are the methods used to minimize loss of associated evidence during recovery?

Bagging in the water

What documentation should be used for underwater evidence?

Photography, slate, buoys