Definition of circumstantial evidence
Circumstantial evidence indirectly proves a fact. It is evidence that requires or allows a trier of fact to make a deduction to conclude that a fact exists. This inference made from a trier of facts supports the truth of asseretion (in criminal law, an assertion of guilt or of absence of guilt). By contrast, direct evidence supports the truth of an assertion directly-i.e., without need for any intervening inference.
Testimony that the witness saw the defendant shoot the victim gives direct evidence. A forensic scientist who testifies that ballistics proves the defendant's firearm killed the victim gives circumstantial evidence, from which the defendant's guilt may be inferred.
Similarly, a witness who testifies that she watched the defendant stab the victim gives direct evidence. A witness who says that she saw the defendant enter a house, that she heard screaming, and that she saw the defendant leave with a bloody knife gives circumstantial evidence.
Circumstantial evidence usually accumulates into a collection, so that each piece corroborates the other pieces (the pieces then become corroborating evidence). Together they support more strongly the inference that the assertion is true.
Forensic evidence supplied by an expert witness is usually circumstantial evidence.
The two areas in which circumstantial evidence is of most importance are civil and criminal cases where direct evidence is lacking.
Circumstantial evidence is used in civil courts to establish or deny liability. It is usually the most common form of evidence, for example in product liability cases and road traffic accidents. Forensic analysis of skid marks can frequently allow a reconstruction of the accident. By measuring the length of such marks and using dynamic analysis of the car and road conditions at the time of the accident, it may be found that a driver underestimated his or her speed. Forensic science and forensic engineering are common as much in civil cases as in criminal.
Circumstantial evidence is used in criminal courts to establish guilt or innocence through reasoning.
With obvious exceptions (immature, incompetent, or mentally ill individuals), most criminals try to avoid generating direct evidence. Hence the prosecution usually must resort to circumstantial evidence to prove the mens rea levels of "purposely" or "knowingly." The same goes for tortfeasors in tort law, if one needs to prove a high level of mens rea to obtain punitive damages.
One example of circumstantial evidence is the behavior of a person around the time of an alleged offense. If someone was charged with theft of money and was then seen in a shopping spree purchasing expensive items, the shopping spree might be circumstantial evidence of the individual's guilt.
Circumstantial evidence is not considered to be proof that something happened but it is often useful as a guide for further investigation. For example, if census records show that several people with the same surname lived at the same address, likely relationships can be inferred from ages and genders but ever since then new methods have been made so that more proof is needed to make the conclusion that sure that people are related.
Circumstantial evidence is normally used in science only to support other forms of evidence.
Circumstantial evidence is used in social studies to reach logical conclusions where other forms of evidence do not exist.
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