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Implied consent

Implied consent 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 Implied consent rather than just read about it. In short: Implied consent is consent which is not expressly granted by a person, but rather implicitly granted by a person's actions and the facts and circumstances of a particular situation (or in some cases, by a person's silence or inaction). For example, if a person is unconscious as a result of injuries sustained during a traffic collision, medical treatment may be provided to that person, despite the unconscious person…

Implied consent — main illustration
Implied consent — illustration

Key takeaways

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

Reference excerpt

Implied consent is consent which is not expressly granted by a person, but rather implicitly granted by a person's actions and the facts and circumstances of a particular situation (or in some cases, by a person's silence or inaction). For example, if a person is unconscious as a result of injuries sustained during a traffic collision, medical treatment may be provided to that person, despite the unconscious person being unable to expressly grant consent for that treatment.

Driving while intoxicated

All U.S. states have driver licensing laws which state that a licensed driver has given their implied consent to a certified breathalyzer or by a blood sample by their choice, or similar manner of determining blood alcohol concentration. Implied consent laws may result in punishment for those who refuse to cooperate with blood alcohol testing after an arrest for suspected impaired driving, including civil consequences such as a driver's license suspension. In 2016, the Supreme Court of the United States in Birchfield v. North Dakota held that both breath tests and blood tests constitute a search under the Fourth Amendment, concluding that requiring breath tests is constitutional without a search warrant, however, requiring more intrusive blood tests involving piercing the skin is not, as the goal of traffic safety can be obtained by less invasive means. Specifically addressing implied consent laws, the court in the Birchfield opinion stated that while their "prior opinions have referred approvingly to the general concept of implied-consent laws" that "there must be a limit to the consequences to which motorists may be deemed to have consented by virtue of a decision to drive on public roads" and "that motorists could be deemed to have consented to only those conditions that are 'reasonable' in that they have a 'nexus' to the privilege of driving". In 2016, People v. Arredondo, the California Courts of appeals debated whether authorities could seize an unwarranted blood sample from an unconscious person suspected of driving under the influence without offending the Fourth Amendment's guarantee against unreasonable searches or seizures. The court ruled that the defendant "consented to such a search in advance solely by operation of the statute in California, which declares that anyone who drives a vehicle in this state is "deemed to have given his or her consent" to blood alcohol testing under specified conditions. Though Arredondo was unconscious at the time his blood was drawn, the court found that the "warrantless search was justified on the consent since California's "implied consent" law states "one who drives a motor vehicle in this state is 'deemed' to consent to blood alcohol testing". Moreover, the court ruled that the extraction was justified by "exigent circumstances, statutorily implied consent, the officer's belief that the extraction was lawful in light of long-standing practice under prior case law and good faith reliance on the implied consent statute". In 1966, the Supreme Court of the United States in Schmerber v. California held that a warrantless blood sample is justified under the Fourth Amendment's pressing circumstances because alcohol in one's blood would be diminished by the body's natural metabolic system if officers were to wait for a warrant. The Fifth Amendment only applies to interrogation and testimony and does not prohibit blood tests. The case resulted in a conviction because it was decided that blood test results do not constitute testimony, proof of a confession or any other communicative acts.

Non-evidential testing In the United States, implied consent laws generally do not apply to Preliminary Breath Test (PBT) testing (small handheld devices, as opposed to evidential breath test devices). For a handheld field breath tester to be used as evidential breath testing, the device must be properly certified and calibrated, evidential procedures must be followed, and it may be necessary to administer an "implied consent" warning to the suspect prior to testing. In most US jurisdictions, participation in a PBT test is voluntary; however for some violations, such as refusals by commercial drivers or by drivers under 21 years of age, some US jurisdictions may impose implied consent consequences for a PBT refusal. For example, the state of Michigan has a roadside PBT law that requires a motorist provide a preliminary breath test; however, for non-commercial drivers Michigan's penalties are limited to a "civil infraction" penalty, with no violation "points". Participation in "field sobriety tests" (FSTs or SFSTs) is voluntary in the US.

Sexual assault

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Implied consent

Start with the simplest possible case. Write down what Implied consent 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 Implied consent 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 Implied consent 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 Implied consent

In research
Implied consent 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 Implied consent 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
Implied consent is common in secondary-school and first-year university syllabi. It links to neighbouring topics American legal terminology, Criminal law, Driving under the influence, so understanding it makes those chapters shorter.
In everyday life
Look for Implied consent 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 Implied consent in 20 minutes

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

Frequently asked questions

What is Implied consent in simple terms?

Implied consent is consent which is not expressly granted by a person, but rather implicitly granted by a person's actions and the facts and circumstances of a particular situation (or in some cases, by a person's silence or inaction). For example, if a person is unconscious as a result of injuries…

Why does Implied consent 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 Implied consent?

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 Implied consent.

Tags

  • American legal terminology
  • Criminal law
  • Driving under the influence
  • Evidence law

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