science

Witness

Witness is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Witness rather than just read about it. In short: In law, a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what they know or claim to know. A witness might be compelled to provide testimony in court, before a grand jury, before an administrative tribunal, before a deposition officer, or in a variety of other legal proceedings.

Key takeaways

Witness belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Witness to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Witness from memory before moving on to harder problems.

Reference excerpt

In law, a witness is someone who, either voluntarily or under compulsion, provides testimonial evidence, either oral or written, of what they know or claim to know. A witness might be compelled to provide testimony in court, before a grand jury, before an administrative tribunal, before a deposition officer, or in a variety of other legal proceedings. A subpoena is a legal document that commands a person to appear at a proceeding. It is used to compel the testimony of a witness in a trial. Usually, it can be issued by a judge or by the lawyer representing the plaintiff or the defendant in a civil trial or by the prosecutor or the defense attorney in a criminal proceeding, or by a government agency. In many jurisdictions, it is compulsory to comply with the subpoena and either take an oath or solemnly affirm to testify truthfully under penalty of perjury. Although informally a witness includes whoever perceived the event, in law, a witness is different from an informant. A confidential informant is someone who claimed to have witnessed an event or have hearsay information, but whose identity is being withheld from at least one party (typically the criminal defendant). The information from the confidential informant may have been used by a police officer or other official acting as a hearsay witness to obtain a search warrant.

Types

A percipient witness (or eye-witness, Lay witness) is one with knowledge obtained through their own senses (e.g., visual perception, hearing, smell, touch). That perception might be either with the unaided human sense or with the aid of an instrument, such as microscope or stethoscope. A hearsay witness is one who testifies about what someone else said or wrote. In most court proceedings there are many limitations on when hearsay evidence is admissible. Such limitations do not apply to grand jury investigations, many administrative proceedings, and may not apply to declarations used in support of an arrest or search warrant. Also some types of statements are not deemed to be hearsay and are not subject to such limitations. An expert witness is one who allegedly has specialized knowledge relevant to the matter of interest, which knowledge purportedly helps to either make sense of other evidence, including other testimony, documentary evidence or physical evidence (e.g., a fingerprint). An expert witness may or may not also be a percipient witness, as in a doctor or may or may not have treated the victim of an accident or crime. A character witness testifies about the personality of a defendant if it helps to solve the crime in question. A crown witness is one who incriminates former accomplices in a crime who following receive either a lower sentence, immunity or also a protection of themselves or/and their family by the court. After they have provided the court with their testimony they often enter into a witness protection program. A secret witness or anonymous witness is one whose identity is kept secret by the court.

Calling a witness

In a court proceeding, a witness may be called (requested to testify) by either the prosecution or the defense. The side that calls the witness first asks questions in what is called direct examination. The opposing side then may ask their own questions in what is called cross-examination. In some cases, redirect examination may be used by the side that called the witness but usually only to contradict specific testimony from the cross-examination. Recalling a witness means calling a witness, who has already given testimony in a proceeding, to give further testimony. A court may give leave to a party to recall a witness only to give evidence about a matter adduced by another party if the second party's testimony contradicts evidence given by the original witness on direct examination.

Testimony Witnesses are usually permitted to testify only what they experienced first-hand. In most cases, they may not testify about something they were told (hearsay). That restriction does not apply to expert witnesses, but they may testify only in the area of their expertise.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Witness

Start with the simplest possible case. Write down what Witness claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Witness before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Witness ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Witness

In research: Witness appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Witness in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Witness is common in secondary-school and first-year university syllabi. It links to neighbouring topics Evidence law, Witness (law), so understanding it makes those chapters shorter.
In everyday life: Look for Witness outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Witness in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Witness means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Witness out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Witness in simple terms?

Why does Witness matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Witness?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Witness.