In its broadest definition, the term evidence refers to anything that is presented to prove something else is true or exists. In the legal system, evidence is any type of proof presented at trial, for the purpose of convincing the judge and/or jury that alleged facts of the case are true. This may include anything from witness testimony to documents, and objects, to photographs. The law provides specific rules of evidence which govern what may and may not be presented at trial. To explore this concept, consider the following evidence definition.

Definition of Evidence


  1. Something legally submitted to a court or other tribunal to prove or ascertain the truth of a matter.
  2. Something that tends to prove or disprove another thing.


1250-1300        Middle English

Gathering and Submitting Evidence

During investigation of a criminal matter, evidence is often gathered for use at trial later. The purpose of gathering various types of evidence is to determine who might be responsible for the crime. This is done by connecting evidence collected with witness statements and other information. There are certain, strict procedures by which evidence must be collected, handled, and transferred, in order for it to be considered valid at trial. The presentation of evidence at trial is governed and regulated by the jurisdiction’s rules of evidence.

Types of Evidence

Evidence comes in many forms, as by its very definition, evidence is any thing presented to prove that something is true.

Scientific Evidence

Scientific evidence used in legal cases is evidence that is determined by scientific testing and/or observation. Because this type of evidence on its own is often indecipherable by judges and jurors, expert witnesses, experienced in the specific field in which the evidence was examined or tested, introduce and explain scientific evidence. Scientific evidence is generally accepted as a neutral source of information, and quite reliable. Scientific evidence commonly used in the modern legal system includes:

  • Fingerprints
  • Hair and fiber comparison
  • DNA analysis
  • Voice identification

Trace Evidence

Trace evidence is a form of forensic or scientific evidence, as it is evidence created when two objects come into contact with one another, or when portions of one object are left behind on another. Very specific methods are used to collect and process trace evidence, in order to maintain its integrity. These methods often involve vacuuming, brushing, taping, swabbing, shaking, and hand picking. Trace evidence may take many forms, including:

  • Plant, mineral, or synthetic fibers
  • Glove prints
  • Hairs
  • Cosmetics
  • Paint chips
  • Glass
  • Botanical materials
  • Footprints
  • Gunshot residue
  • Explosives residue
  • Volatile hydrocarbons

In order for trace evidence to be useful, investigators must have sample items from the suspect by which to compare it. For example, footprints are most useful if the suspect owns a pair of boots with tread to match the prints.

About DNA Evidence

Deoxyribonucleic acid (“DNA”) is the basic building block of life, and exists in every cell of all living organisms. Modern technology has led to the ability to examine an individual’s DNA, which has a very specific and unique pattern. DNA evidence can be used to identify or exclude individuals as suspects in a crime, as forensic investigators can examine DNA left at a crime scene, and compare it to DNA samples collected directly from a suspect to determine whether the crime scene sample belongs to the suspect or not.

DNA evidence is used as a highly accurate method of proving the guilt or innocence of suspects in some cases. In order to challenge or disprove DNA evidence, the opposing party must usually bring into question the procedures used to collect and test the evidence.

Physical Evidence

Physical evidence, sometimes referred to as “material evidence,” or “real evidence,” is any tangible object that is used to prove a fact of the case. Physical evidence includes objects, as well as documentation. Many items of physical evidence serve a joint purpose, as both physical and scientific evidence. For example, examination of a knife used in an assault (physical evidence) may yield scientific DNA evidence as well.

Testimonial Evidence

Testimonial evidence is that given by a witness under oath. Such testimony may be given verbally or in writing, under penalty of perjury. Any witness who is not testifying as an expert witness is generally limited to providing testimony only of those things of which he has personal knowledge, and may not interject opinion. Testimonial evidence is an important part of the legal process, though the opposing party may introduce additional testimony, or other evidence, to disprove or discredit a witness’ testimony.

Circumstantial Evidence

Circumstantial evidence is evidence that does not directly prove a fact, but requires some amount of reasoning, or inference, to make a point. While some people view circumstantial evidence as weak, or ineffective, it is possible to submit one or more circumstances for which the most probable conclusion leaves little doubt as to a fact of the case.

For example:

Roger is accused of breaking into a woman’s home and raping her. Although the woman cannot identify the man, as it was dark, and he wore a mask, the prosecution shows that Roger had previously made threats to the victim, his footprints were found outside the victim’s back door, fibers found caught in the broken window match those of Roger’s jacket, and Roger had been seen by neighbors in the neighborhood earlier that day. While all of these are circumstantial evidence, they add up to a logical conclusion that Roger committed the crime.

Hearsay Evidence

Hearsay evidence is a statement made out of court, whether verbally or in writing, that is introduced to prove the truth of whatever the statement asserts. In most cases, hearsay evidence is testimony by one person of what another person said. Hearsay evidence is not considered reliable, since the person who actually made the statement is not available to be questioned. Because of this, hearsay evidence is not usually accepted at trial. There are exceptions, however. For example, if a robbery victim stumbled up to Allison and said, “Victor robbed me!” before falling down unconscious, Allison’s testimony of what the victim said cannot be used to prove that Victor committed the robbery. Her testimony could, however, be used to prove that the victim was still alive and able to speak at that time.

Exculpatory Evidence

Exculpatory evidence is any evidence that is favorable to, or tends to exonerate, the defendant in a criminal proceeding. In the 1963 landmark U.S. Supreme Court case Brady v. Maryland, the Court determined that the prosecution is required to provide a defendant with any exculpatory evidence it has in its possession, custody, or control, before the defendant enters a plea, or as soon as the evidence comes into its possession, custody, or control. This includes any exculpatory evidence held by the investigatory team, such as police officers, investigators, and crime labs.

For example:

Bob is found murdered outside his home, and police find Malcom passed out in his car some miles away, a bloody knife on the ground near the vehicle. While Bob has been arrested and charged with the murder, the investigation turned up testimony of a witness who saw someone who was not Malcom fighting with Bob at the scene of the crime, but was too afraid to come forward.

Although police investigators doubt the validity of the witness’ statement, his testimony is exculpatory evidence that places doubt on Malcom’s guilt. The prosecutor is required to provide Malcom, or his attorney, this witness’ testimony.

Rules of Evidence

Federal and state rules of evidence govern how facts are proven, as well as how inferences may be made from facts and evidence introduced at trial. Laws governing rules of evidence stem from a concern over the validity of certain types of evidence, and whether the presentation of certain evidence might lead a judge or jury to jump to conclusions that are not necessarily valid. Rules of evidence typically revolve around the issues of reliability, relevance, efficiency, unfair surprise, and overall fairness to the proceedings.

To this end, the judge in a criminal proceeding has the power to exclude any evidence that poses a great risk of creating unfair prejudice due to a confusing, repetitive, or inflammatory nature. This is done to help ensure the jury receives a broad range of evidence that is not unnecessarily confusing.

Scott Peterson and the Circumstantial Evidence

On Christmas Eve, 2002, 27-year old Laci Peterson was reported missing by her husband of 5 years. Husband Scott Peterson told police that his wife, who was 8 months pregnant at the time of her disappearance, was nowhere to be found when he returned from a fishing trip 80 miles from home. While no indication of where the young woman might have gone existed, certain facts arose leading investigators to suspect Scott Peterson may have been involved in her disappearance.

Four months after she vanished, the badly decomposed remains of Lacy and her unborn child washed ashore in Richmond, California, near the marina at which Scott Peterson claimed he spent the day fishing the day Laci vanished.

Although prosecutors strongly suspected Scott Peterson was guilty of murdering his wife, there was little direct evidence connecting him to the crime. What the prosecution did have was a whole string of circumstantial evidence, including inconsistencies in Peterson’s story, his admitted affair, and a 6-inch long dark hair found on a pair of pliers in Peterson’s boat. Although the defense attempted to explain away each item of circumstantial evidence, in an effort to create reasonable doubt in the minds of the jury members, Peterson was convicted of first degree murder of his wife and unborn child.

Scott Peterson was sentenced to death, and transferred to death row in California’s San Quentin prison, where inmates spend an average of 25 years before execution.

Related Legal Terms and Issues

  • Expert Witness – A witness possessing training, education, skill, or experience in a specific subject, which is beyond that of the average person, who is allowed to give an opinion at trial.
  • Perjury – The willful telling of an untruth, or the giving of false testimony, after having taken an oath.
  • Death Row – A prison housing unit reserved for inmates sentenced to be put to death.