What are the four types of evidence in a criminal investigation? A: The four types of evidence in a criminal investigation are physical, documentary, demonstrative, and a testimony. What are individual characteristics? Give an example of an individual characteristic? A: An individual characteristic are things associated with a common source with a high degree of certainty. An example of an individual characteristic is the ridges in a fingerprint sample. What is the difference between individual characteristics and class characteristics? A: Individual characteristics are associated with one source, class characteristics are associated with a group of sources. What are physical and chemical properties? Give an example of each. A: Physical properties are describing a substance without referring to another substance; chemical properties are what will happen when a substance reacts with another.
An example of a physical property is like glass, and describing its size, shape, color, etc. An example of a chemical property is like when you test one chemical with another to test and see if they are legitimate drugs or not. What do forensic scientists do to collect and preserve soil samples? A: Forensic scientists collect a tablespoon or two of soil and take great care to preserve the samples. For example, if there is a soil sample on a shoe, the entire shoe will be taken to the lab, rather than just the soil sample.
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? A: I think forensic scientists are so careful so that they can give accurate results to a courtroom and find the suspect of the crime, if they weren’t so careful, they may get the wrong guy or not get the criminal at all. Which type of evidence do you think is most useful in an investigation? Why? A: I think physical evidence is the most useful in an investigation because it gives clear and concise facts about what happened based upon what you see. Why do you think that forensic scientists continue to look for class characteristics given their limitations? A: I think forensic scientists look for class characteristics so that they can pin multiple things to one source and hopefully find the criminal.