Flashcards Forensic Science Flashcards: Blood, Patterns, Firearms, and Digital Evidence

30 flashcards covering key forensic topics from blood analysis, pattern interpretation, hair and fiber evidence, firearms, ballistics, and digital evidence handling.

What is the role of luminol in crime scene blood detection?

It reacts with latent blood not visible to the naked eye, producing a luminescent glow under low blue light to reveal it.

What does latent blood evidence mean?

Blood evidence that is not visible without chemical enhancement, such as luminol, and may be cleaned up but can still be detected.

How does blood evidence connect to DNA and identification?

Blood contains DNA for analysis; blood type can aid identification; patterns from blood spatter can help reconstruct events.

Name the three main categories of blood stains.

Passive patterns, transfer patterns, and spatter patterns.

What effect does surface texture have on a 90-degree blood drop?

Smooth surfaces yield a round, even stain; textured or rough surfaces create scalloped or spiky edges and satellite stains.

What are the edge characteristics used to describe bloodstains?

Smooth, scalloped, or spiky edges.

What are satellite stains in bloodstain analysis?

Smaller stains that originate from a parent stain due to disruption or movement of the blood.

What is feathering in blood patterns?

A transition from dark to light edges indicating movement of blood across a surface.

What are drag marks in bloodstain patterns?

Trails left by movement of a bleeding person or object through blood, showing direction of travel.

What do flow patterns describe?

The volume and direction of blood affected by gravity as it moves downward on surfaces.

What are saturation and pooling patterns?

Saturation refers to the amount of blood absorbed by a surface; pooling refers to accumulation of liquid blood on non-porous surfaces with slower drying.

What is serum separation in a blood pool?

The edge where plasma separates from red blood cells as the pool ages.

What is forward spatter and back spatter?

Forward spatter travels in the direction of the applied force; back spatter travels toward the source, opposite the force.

What is the area of convergence?

A two-dimensional area where the long-axes lines of several stains intersect, pointing to the origin of the blood spray.

How is the angle of impact calculated for a bloodstain?

Angle = arcsin(length/width) of the stain's long axis divided by its width; results are in degrees.

What is the area of origin?

The three-dimensional point from which the blood originated, inferred using the angle of impact and distance from the convergence area.

What does the adage 'forensic science is the art of observation governed by science' mean?

Patterns are interpreted with scientific reasoning; there is no crystal-ball certainty; requires training and experience.

What is a passive drip pattern?

Blood dripping under gravity without external forces after initial deposition, often layering with other stains.

What is a swipe pattern?

A transfer pattern where blood is on an object moved across a surface, leaving a linear or curved trail.

What is a cast-off pattern?

Blood projected off an object in motion, creating a pattern that can run up walls or across surfaces.

What is a void pattern?

An absence of stains within a blood pattern indicating an object or person was present and then removed.

Why are shoe and tire prints useful in forensics?

They provide a comparable pattern to identify shoe type, size, or brand and help place a suspect at a scene; requires preservation and databases.

What can bite mark evidence be used for?

Images and casts of teeth are compared to suspect dental records; used by forensic dentists to link or exclude suspects.

What are the components of a cartridge?

Bullet (projectile), casing, powder, primer; the firing pin ignites primer, which ignites powder to propel the bullet.

What does 'caliber' refer to?

The inside diameter of the gun's barrel, measured in inches or millimeters, used to describe the firearm's size.

What is rifling and why is it important?

Spiral grooves inside the barrel that spin the projectile for greater accuracy, leaving distinctive marks on bullets.

Why are bullet striations important?

They create unique markings on a fired bullet that can be matched to a specific firearm through ballistic analysis.

What is NIBIN?

The National Integrated Ballistic Information Network, ATF database for comparing cartridges and bullets to link to firearms used.

What does gunshot residue (GSR) testing indicate?

Presence of residue on hands or clothing suggesting recent firing or handling of a firearm; not a definitive identifier of the weapon.

What is a Faraday bag used for in investigations?

A shielded container that blocks electromagnetic signals to prevent remote erasure of digital evidence from devices like cell phones.