In either a civil lawsuit or criminal prosecution, evidence is needed to meet the burden required to win the case. Evidence comes in many forms, including testamentary, documentary, physical, and demonstrative. Some evidence is considered direct, or primary, evidence, while other evidence is circumstantial, or indirect, evidence. Evidence that only creates an inference or that does not directly lead to a conclusion of fact is known as indirect evidence.
The required burden of proof will vary by jurisdiction. In the United States, the burden of proof in a criminal trial is "beyond a reasonable doubt," while the burden of proof in a civil lawsuit is "beyond a preponderance of the evidence" in almost all cases. A precise definition for both continues to elude even legal scholars; however, it is clear that the burden of proof in a criminal trial is significantly higher than that of a civil lawsuit. As a result, indirect evidence is more likely to be sufficient to support a determination of liability in a civil lawsuit than a verdict of guilty in a criminal trial.
In a criminal prosecution, indirect evidence may be considered more valuable when the totality of the indirect evidence leads to a conclusion. If, for example, a witness in a robbery trial can testify that she personally saw the defendant pull out a gun and rob a store owner, that would be direct evidence. If, on the other hand, she can only testify to seeing the defendant enter the store and leave the store at the time the store was allegedly robbed, that is only indirect evidence and unlikely to be enough to convict the defendant of the crime. If she can also testify that she heard screams from inside the store, saw the defendant leave with a gun in his hand, and entered the store herself shortly thereafter and was told it had just been robbed, then that is a collection of indirect evidence that, in totality, may be more likely to lead a jury to believe that the defendant committed the crime.
In a civil lawsuit, indirect evidence is used more frequently and often more successfully due to the lower burden of proof. In a car accident case, for example, the speed at which the driver of a car was driving may be determined by expert testimony based on a forensic analysis of skid marks, road conditions, and impact tests. Unless someone was at the scene with a radar gun pointed at the car to provide direct evidence of the speed, indirect evidence will be used and likely accepted.