Evidence is information offered in court to prove or disprove a fact and to show that a crime was committed. It is shown in court as an item of proof, to impeach or rehabilitate a witness, and to determine a sentence. Evidence can come in the form of weapons, documents, pictures, tape recordings, or exhibits. There are four different types of physical evidence that are considered in court. The first are the fruits of the crime, which is what the suspect gets out of the crime. The instrumentalities of the crime are the means by which the defendant actually committed the crime, such as by a gun, knife, or crowbar. The third type of physical evidence is contraband, which is a crime by possession. Mere Evidence is any other type of physical evidence. Two other types of evidence are direct and circumstantial. Direct evidence proves a fact directly, and often comes from eyewitnesses. Circumstantial evidence requires the court to make an inference or assumption about the case. Evidence offered in court must be competent. It is considered incompetent if offered by an incompetent witness, obtained in violation of constitutional provisions, or if it is not properly prepared and safeguarded through the chain of custody.
             According to the book Hard Evidence by David Fisher, "the chain of custody is a legal standard which prescribes the handling and documentation necessary for specimens and testing to be admissible as evidence in a court of law. Admissibility of laboratory testing results as court evidence will be compromised if Chain-of-Custody protocol is not strictly followed by all who handle, store, test, and report on such specimens." The chain of custody begins when the evidence is collected at the crime scene and continues until the evidence is officially disposed of. Each person who has custody of the evidence is responsible for its preservation and safekeeping. Each piece of the chain of evidence must include sp...