What type of evidence should be collected first?
In order of collection, the most fragile evidence must be collected first. A crime scene investigator may start with hairs and fibers and fingerprints and then work his or her way through the evidence, peeling back one layer at a time.
What do blood patterns tell investigators?
Bloodstain pattern analysis (BPA) is the interpretation of bloodstains at a crime scene in order to recreate the actions that caused the bloodshed. Analysts examine the size, shape, distribution and location of the bloodstains to form opinions about what did or did not happen.
What is the fastest that free falling blood can travel?
-the ration of the density of blood to the density (mass of the same unit volume) of water. –free falling blood will fall at a speed of 25.1 plus or minus 0.5 feet per second. -like all liquids, blood is held together by cohesive force producing a skin like surface resistant to penetration or separation.
How can too much blood negatively affect a crime scene investigation?
Large amounts of blood, such as if the person bled to death or was so severely injured that the resulting blood spatter was extensive, can often yield less information than several well-defined spatter patterns. Too much blood can disguise spatter or make stain patterns unrecognizable.
When first arriving at a crime scene you do not see blood What should you do?
When first arriving at a crime scene, you do not see blood. What should you do? Spray the area with Luminol, powder mixed with hydrogen peroxide to detect hemoglobin left behind in blood.
What force must exceed the surface tension of blood in order for it to free fall?
gravitational force
At what height does a droplet of blood reach terminal velocity?
The velocity of the falling blood will continue to increase until it reaches terminal velocity, 9.8 ms-2, the downward pull of gravity. Studies done by MacDonell on 0.05 ml drops of falling blood showed that terminal velocity would occur when the drop falls 25.1 feet (7.7m).
When a forensic investigator comes across possible blood evidence at a crime scene what 3 questions will they ask?
What three questions should the investigator answer when examining an apparent dried bloodstain? -is it blood? -is it human or animal? -what is the blood type?
What are the four phases of impact?
When the blood falls from the source, the circular droplet essentially splashes out of itself to create the different patterns that are visible to the human eye. There are four phases of impact: contact and collapse, displacement, dispersion, and retraction.
How is blood evidence detected at a crime scene?
Unfortunately, some crime scene investigators use luminol as their first choice for detecting blood. When searching for blood at a crime scene, especially blood that may have been cleaned up, the investigator should first use a high intensity light to search for any traces of blood.