When it comes to law, evidence can be of different types. While written documents are produced as evidence in some cases, fingerprints collected from a crime scene constitute another type of evidence. Sworn testimony of a witness is also a form of evidence. A CCTV footage from the crime scene can also be used as evidence. In short, evidence is used to prove certain facts that are relevant to the case. Evidence can be of different types that are classified on the basis of various factors like relevance, nature, etc. While documentary evidence refers to documents (like wills, contracts, photographs, and letters), testimonial evidence denotes the statements offered by witnesses. Physical evidence includes tangible things that are related to the issues of the case. So, a murder weapon is physical evidence. According to Black's law dictionary, physical evidence is defined as, the term that is given to the evidence that can be seen in a court room. Such objects can be anything from a huge vehicle to microscopic items. So, many of them cannot be produced in the court house. Physical evidence is a tangible thing that is directly involved in the case. Such evidence is introduced during the trial with the intention of proving the facts in issue. As the name rightly suggests, it is the physical characteristics of the thing that is taken into consideration, rather than its contents. A letter produced as evidence in a murder trial is documentary evidence if its content is linked to the facts of the case. A letter splattered with the victim's blood is physical evidence in a murder trial. Likewise, a written contract is a physical evidence to prove the existence of a contract and its terms and conditions. Physical evidence is direct evidence, as it proves or disproves a fact directly. A defective product that is introduced as physical evidence is direct evidence to prove the defect in a products liability case. The term real evidence is often used in place of physical evidence. It is also considered as a type of physical evidence; the other being demonstrative evidence, which is a representation of the actual thing. It can be a model, a copy, or a replica of the original. A diagram of the crime scene is demonstrative evidence. Such evidence is often used to illustrate or demonstrate the testimony of a witness. For example, a person got injured while operating a defective product. He files a product liability lawsuit and produces the defective product as evidence to prove that the injury was actually caused by that product. This is considered real evidence. If the plaintiff produces the diagram of the product to compare it with the defective product, the former is demonstrative evidence. Usually, objects found at a crime scene are introduced as physical evidence, as they can be used to prove the facts of the case. In fact, such objects are considered as real evidence. Physical evidence that can be collected from a crime scene include articles splattered with blood, murder weapon, firearm, tools used for burglary, vehicle used by the offender, tire marks, footwear and footprints, articles with fingerprints, illicit drugs, chemicals, medicines, traces of explosives, dead bodies, biological material (like blood, saliva, semen, hair, skin cells, etc.), documents, firearms, etc. In short, physical evidence can be anything that is generated (like blood samples) as a result of the crime. It could be a tool used for committing the crime (like a knife or gun). It could be an object possessed by the offender (like illicit drugs). In some cases, gruesome or gory objects are admitted as evidence if their value (for the prosecution) exceeds their prejudicial effect (on the defendant). The evidence that can be collected from a crime scene may vary according to the nature of the crime. In case of a crime, real evidence can be collected from the crime scene, the person of the perpetrator, from his home and vehicle, and from the body of the victim. Such evidence plays a major role in interpreting the facts, reconstructing the events, and determining the nature of the crime. Crime scene investigation will also lead to other evidence and helps in identifying the offender(s). So, such evidence has to collected and maintained in a proper manner, so as to preserve the integrity of the objects. In case of real evidence, the object itself is the evidence. If a murder weapon is real evidence, photographs of the crime scene are demonstrative evidence. Physical evidence has to be authenticated, so as to prove that it is genuine. It can be done through testimony of a witness or through the opinion of an expert witness. This is one of the important requirements for admission of real evidence. It must be proved that the object is connected to the facts of the case, and it is useful for proving some facts that are relevant to the case. So, someone must testify that the article that is introduced as evidence is related to the crime and is obtained from the crime scene. In some cases, authentication is not required. Certified copies of public records, public documents, and official publications, newspaper articles, etc., come under this category. In case of criminal trials, the police officer who collected the objects from the crime scene is responsible for getting them authenticated. If admitted, such evidence may prove detrimental for the accused. So, the defense counsel may try to prove that the object is not relevant to the case, or it is being tampered with or contaminated. In short, physical evidence includes real evidence and demonstrative evidence. While real evidence denotes actual objects, demonstrative evidence includes representation of the objects (such as models and photographs). Physical evidence must be authenticated with witness testimony or by proving that it has been held in an unbroken chain of custody.