What Are Some of the Different Types of Evidence Used in Criminal Investigation?

The relevance of evidence answers the question of how much credibility should be given to a theoretical hypothesis; in effect it serves the purpose of authentification of the grounds for suspicion. Directly relevant evidence is that which is established by logical causation. For instance, if a person gives testimony that he saw a murder committed at a certain place and time and gives a description of the suspect, that evidence is considered directly relevant. If another person not at the crime scene comes forward with information that the first witness who has provided directly relevant evidence has a history of pathological self-aggrandizement through embellishment and so therefore raises questions about the reliability of his testimony, that is an example of indirectly relevant evidence. Also known by the term ancillary evidence, its appearance may have the power to force a reconsideration of the entire original hypothesis.

Documentary evidence is essentially any paperwork or computer records that may be useful in an investigation. The competence and credibility issues facing documentary evidence includes determining and obtaining authentification of any written documents in such a way that they would be admissible in court: certified records, official documents, published reports. In addition, the evidence would need to be examined to confirm that it is actual witness testimony and not merely inadmissible hearsay or opinion. Credibility cannot simply rest upon an assumption of competence; there must also be objective standards in place that could be potentially met regardless of the subjective trust between individuals and the inference of reliability.

Dissonant evidence occurs in two types. The contradictory form of dissonant evidence is when events occur that simply cannot happen together in any kind of logically plausible way. Inferential issues are effectively undone by contradictory dissonance, although it is clear that irrational beliefs can cause people to cling to certain contradictory evidence. Of course, irrational people actually are capable of drawing inferences from contradictory evidence. Conflicting evidence presents a more difficult proposition, however, as it calls for one to infer upon evidence that may not be wholly credible, or that may call upon one to make an inference that is not entirely well founded based on their belief. The inference that is made in dissonant evidence that is merely conflicting and not entirely contradictory often requires a leap of faith that may fly in the face of rational expectations, but still remains grounded so that it is not entirely irrational like the stubborn belief in contradictory evidence.

Hedging in probabilistic terms is often a necessary component in analyzing evidence because inferential conclusions should also be partnered with some type of axiomatic reasoning. In other words, deductions based on probability only deserve access if they are relative to a certain inductively axiomatic condition. Since these axiomatic conditions are open to a wide variety of theories subjectivity is also conditional, either through a prior distributive channel or through inferences that are not contradictory to the axiom. It is often necessary to hedge because the deductions will not or cannot always reach perfect agreement with axiomatic conditions, however.