Physical properties usually refer to the characteristics which are not related to the chemical composition of an object. For instance, in this case, I will use a paperclip. A criminalist could use the color, mass, electrical conductivity, density and hardness as the physical properties of the paperclip to differentiate the piece of evidence from types of the same item(Dutelle, 2016). On the other hand, chemical properties involvethe change of a kind of a substance to another form. The criminalist would use the reactivity, of the paper pin for instance to make the difference. Rust formation refers to a chemical change since rust is a separate kind of matter different from the iron, water, and oxygen that are present before the creation of the rust.

As mentioned earlier in the previous module, class characteristics usually are not exclusive to a specific item; hence they put physical evidence to a group of objects(Horswell, 2016). On the contrast, individual evidence refers to the kind of proof that is exclusive to a particular individual or unique object which can be possessed by only one individual.The individual characteristics may narrow reduce the available evidence to a single source. For example, blood that is recovered from a crime scene whose test indicates that it is blood type A, which is a class characteristic could be from any of the many individuals sharing blood type A, therefore; the person remains just a suspect(Dutelle, 2016). However, if it is the DNA that is an individual characteristic tested from the particular suspect and the recovered blood and they match then it could be narrowed that the person was involved in the crime. The mostly used individualizing evidence types are DNA and fingerprints, as no people existing with similar prints(Horswell, 2016). Shoeprints and tire tracks are unique and therefore could be part of the individual characteristics.

 
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