Unit 3 text questions

Sandra Cash March 7, 2011 Forensic Science Unit 3 Text Questions Review Questions 
What are the four types of evidence in a criminal investigation?
The four typed of evidence in a criminal investigation are physical evidence, documentary evidence, demonstrative evidence and testimony.
What are individual characteristics? Give an example of an individual characteristic?
Individual characteristics are properties associated with a common source to a high degree of certainty. An example of individual characteristics is that forensic scientists may look for in a criminal case is the ridge characteristics of two fingerprint samples.
What is the difference between individual characteristics and class characteristics?
Class characteristics are those that can only be associated with a group and not a single source. Where individual characteristics are properties associated with a common source to a high degree of certainty.
What are physical and chemical properties? Give an example of each.
Physical properties are those that describe a substance or object without referring to any other substance. For example physical properties of glass might be its weight, size, color, and volume.
Chemical properties are those that describe what happens when a substance reacts with another substance. For example, when the drug heroin comes into contact with the Marquis reagent chemical it turns purple.
What do forensic scientists do to collect and preserve soil samples?
Soil samples are typically collected from the crime scene within a 100-yard radius at various spots. Also if soil is found on the bottom of a shoe, for example, the soil is left on the shoe and the entire shoe is taken to the crime lab. The object must also be stored in such a way that any pieces of dirt that may fall off the object are retained.
Critical Thinking Questions 
Why do you think forensic scientists are so careful that the tests they do are sensitive, reproducible, and specific? What might happen if they were less careful about this?
I think forensic scientists are so careful that the tests they do are sensitive, reproducible and specific, because this helps to ensure that a test is valid and it helps to get the most information out of the evidence. If they were less careful about this the test would not be valid, and they would not get very much information out of the evidence.
Which type of evidence do you think is most useful in an investigation? Why?
I think the type of evidence that is the most useful in an investigation is physical evidence. I believe this because physical evidence can help forensic scientists understand what happened at a crime scene and help them identify who is responsible for a crime. Plus physical evidence may provide class and individual characteristics.
Why do you think that forensic scientists continue to look for class characteristics given their limitations?
I think forensic scientists continue to look for class characteristics, because it helps investigators piece together the crime, especially in the courtroom.
What do you think would be some of the challenges in collecting and preserving impressions? Why?
I think that some of the challenges in collecting and preserving impressions would be when the impressions are found in the dust on smooth surfaces. I think this because I have would have a hard time using clear tape to lift the impression. I tried to do this once with a finger print from a detective kit when I was a kid and it is really hard to do!
If you were on a jury, do you think you would expect individual characteristics in the evidence? Why or why not? What effects might it have if individuals expect to have individuals characteristics presented?
If I was on a jury, I would not expect individual characteristics in the evidence, because characteristics in the evidence may not be available at all crime scenes. The effects that might be if individuals expect to have individuals characteristics presented is that they may not see that the case is strong enough to say that the person is guilty, even though the person might actually be guilty of the crime.

Unit 3 text questions

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