I have given some thought to the proposition: How would the law change if you could cast a spell compelling someone to tell the truth? Below are my thoughts on the matter. I am going to begin with a 10,000-foot overview of the law, much of which you are probably familiar with. Nevertheless, it will assist me in providing a comprehensive discussion of how the law would change. For ease of discussion, I am going to speak of the law generally and not distinguish between state and federal law.

Overview

We begin with the Constitution, which separates the roles of the branches of government and articulates some enumerated rights of the people. After that, we can divide the law up into six categories as follows:

Criminal Law

This is the law governing disputes between the government and individuals.

Tort Law

This is the law of redress for injuries caused by others. Some torts are intentional (e.g., defamation and battery), while others are based on theories of negligence (e.g., medical malpractice, products liability, and slip-and-fall accidents). Interestingly, much of tort law does not come from statutes. Instead, most of it comes from the common law that predated the nation and is effectively "judge-made." The Supreme Court(s) occasionally recognize new causes of action. For our purposes, I am going to place most constitutional law here as well. If the government is infringing upon your rights and you sue, that is basically a tort.

Contracts

I am going to place family law (e.g., marriage and divorce) in this category as well. The most important thing to note about contracts is that they permit arbitration, which is a wholly different category of "court" for adjudicating disputes. In a world with spells, parties could agree by contract to have disputes resolved by a court of wizards, for example.

Wills, Trusts, and Estates

Pretty self-explanatory: Who gets my stuff after I die?

Administrative Law

I am going to use this term much more broadly than it is commonly understood to cover any matter overseen by the government, such as the FAA, Patent Office, EPA, SEC, SSA, Postal Service, and so on. I am also going to include bankruptcy and tax law here for good measure. Administrative law is essentially a combination of criminal law, torts, and contracts. In short, we have decided that there are some areas in which economies of scale and efficiency are gained through the government's centralized management.

Judicial Procedures

These are the laws concerning how we adjudicate all of the above. This area includes the Rules of Civil Procedure, Rules of Criminal Procedure, Rules of Appellate Procedure, and Rules of Evidence. Some of the rules are common law (unwritten and developed by judges), such as the doctrine of res judicata. This doctrine essentially provides that I cannot sue you twice for the same thing. Another example, closer to the nitty-gritty aspects of litigation, is the doctrine that issues not timely raised are waived. There is also a category of constitutional law that is procedural. For example, if the government conducts an illegal search of a premises, the fruits of that search may be procedurally suppressed.

The Law Post-Magic

These are my thoughts and questions as you build your world around the idea of a "truth spell." I am assuming that truth spells compel a person to answer truthfully only in response to a question. I am also assuming that truth spells are not cost-prohibitive, can be readily obtained, and can be administered to the same person indefinitely. If they are expensive, difficult to obtain, or can only be administered to a person a finite number of times, then the discussion below changes in degree. I believe that, if you systematically answer the questions below, you will develop a good framework for a world in which truth spells are possible.

• Constitutional Law.

Does your constitution address the ability to cast a truth spell? Do people have a right to be free from the government's "unreasonable use of a truth spell"? Does the constitution specify which branch of government has the authority to regulate truth spells?

• Criminal Law.

I assume that it would be a crime to cast a truth spell on a person without that person's consent. There are major implications for criminal trials, but I will discuss those below under judicial procedures. Another issue to consider is when law enforcement may use a truth spell. Can it only be used during a judicial proceeding? Does its use require a warrant? Can it be used with the accused's consent, like a polygraph test? Can a truth spell be used in exigent circumstances (e.g., "There is a nuclear bomb somewhere in New York")?

• Torts.

Is it an intentional tort to use a truth spell on another person without that person's consent? If so, how would damages be calculated? For example, if a woman casts a truth spell on her boyfriend to ascertain his intentions and discovers that he is only with her until someone better comes along, what damages, if any, should be available to compensate him for the loss of autonomy caused by the truth spell? These are not easy questions because they point to a foundational principle of your society: Is compelled truth-telling considered a social good? For example, there is currently a rule of evidence that prohibits a person from introducing evidence of remedial measures taken by the opposing party after an accident. Thus, if you slip on my floor and I later install carpeting to prevent future falls, you generally may not introduce that installation as evidence that I knew the floor was hazardous. This rule is based entirely on the premise that society wants to encourage the prevention of future injuries. Does your society want to encourage the use of truth spells and the truth generally? Or is a truth spell a theft of autonomy? In our society by contrast, autonomy and privacy are considered the higher goods.

• Contracts.

Contracts would change profoundly. I believe the situation would be somewhat analogous to modern credit scores. Parties could still enter into contracts that did not require one or both sides to submit to a truth spell, but they would likely pay a premium for the additional risk associated with such arrangements. Otherwise, most contracts would likely require each party to submit to a truth spell either before entering the agreement or when a dispute arises concerning the parties' representations, intentions, or performance under the contract.

Marriage contracts would likely operate much the same way. After all, would most people enter into a marriage without knowing whether the other person was genuinely committed to them? It is difficult to imagine annulments in a world where truth spells exist because it is often premised on the idea that one party was misled when entering the marriage. Although all U.S. states currently permit no-fault divorce, some states still allow divorce based on fault, such as adultery, abandonment, or cruelty. Truth spells would obviously become relevant in such proceedings.

Family law also includes custody disputes, paternity actions, and adoptions. You would need to decide whether truth spells work on children and, if so, whether they can be administered to children.

• Wills, Trusts, and Estates.

Typically, disputes in these areas concern the value of property or assets. The testator (the person who created the will or trust) is usually deceased and therefore cannot be subjected to a truth spell. There are sometimes lawsuits alleging that an heir took advantage of a person with diminished capacity and induced that person to alter a will despite lacking the legal capacity to do so. There are also lawsuits alleging that an executor or trustee breached a fiduciary duty owed to heirs or beneficiaries. Truth spells would likely play a significant role in these proceedings.

• Administrative Law.

The government would likely require truth spells to prevent fraud, waste, and abuse of public funds, as well as to promote public safety. If you want a government contract, want to engage in a permitted or licensed activity, or wish to receive disability benefits, you may be required to submit to a truth spell. I could envision a world that is far more bureaucratic because many transactions would need to occur in person so that the government could administer and verify truth spells. Or perhaps it will be like a red v. blue divide where some states require truth spells to live and others do not.

I think the most interesting area of change would be corporate law. Incorporation shields business owners from personal liability for the actions of the corporation. There would be a constant game of cat and mouse in determining which person within a corporation should be subjected to a truth spell. Is it a board member? The CEO? An employee? The owner? The answer could significantly affect the outcome of disputes and investigations.

• Judicial Procedures for Criminal Cases.

In a criminal case, a person is charged by a prosecutor or indicted by a grand jury. The defendant then appears at an arraignment, where the charges are formally presented. The court may also impose terms and conditions of release. Between the arraignment and trial, there are typically pretrial motions challenging the indictment, the existence of probable cause, the admissibility of evidence, or the terms and conditions of release.

We currently recognize a right against self-incrimination, and a defendant is not required to testify at his or her own trial. Would we continue to recognize that right if a simple truth spell could establish guilt or innocence? A defendant has the right to confront witnesses, but does a person have a right to compel a person to submit to a truth spell? Would law enforcement officers and investigators be required to submit to a truth spell when testifying? What about victims and other witnesses? How would truth spells operate when applied to individuals suffering from mental illness?

If no one is required to undergo a truth spell in a criminal proceeding, then the law might not change dramatically. However, a significant question remains: should a court be permitted to draw an adverse inference from a person's refusal to submit to a truth spell?

• Judicial Procedures for Civil Cases.

Civil cases follow a similar structure. A lawsuit begins with a complaint, which notifies a person that he or she is being sued, followed by an answer responding to the allegations. A defendant may file a motion to dismiss. The existence of truth spells would not substantially affect this stage because the court generally assumes that all well-pleaded allegations in the complaint are true when deciding such a motion.

Assuming the case survives a motion to dismiss, the parties enter the discovery phase. The Rules of Civil Procedure govern discovery, which includes requests for admissions, depositions, interrogatories, and document production. You would need to decide whether truth spells constitute a separate category of discovery or whether they are simply incorporated into existing procedures, such as depositions.

In civil litigation, the parties frequently negotiate or seek court orders limiting the scope of discovery. Thus, there would be many court arguments about who is subject to truth spells and who is not. After discovery, the parties often move for summary judgment. At that stage, the court determines whether there is a genuine dispute of material fact and whether the moving party is entitled to judgment as a matter of law. Truth spells would generally not play a substantial role in that analysis because the court is not supposed to make credibility determinations and is required to view the evidence in the light most favorable to the non-moving party.

• Trials.

Civil and criminal trials are largely the same, aside from differences in jury size and the applicable burden of proof. Both types of proceedings are governed by the Rules of Evidence. Here are some of the key areas to consider:

• Jury Selection. Prospective jurors would likely be asked whether they have ever been subjected to a truth spell and whether they would be inclined to distrust testimony that was not given under the effect of a truth spell.
• Privilege. A person generally cannot be compelled to disclose communications made to an attorney, spouse, or clergy member. Some jurisdictions also recognize privileges covering communications with therapists and medical professionals. Presumably, a person subjected to a truth spell would still be entitled to refuse to answer questions concerning privileged communications. What mechanism actually stops them from answering the questions about privileged information?
• Competence. We expect witnesses to be competent to (1) understand the questions and (2) answer them truthfully. Children, people under the influence, and the mentally ill are often found incompetent to testify. You would have to decide how a truth spell works on these categories of people.
• Personal Knowledge. A witness may testify about a matter only if the witness has personal knowledge of it. This is often referred to as a "foundation" objection. Simply because a person can be compelled to tell the truth does not mean that the person has an adequate basis for what he or she truly thinks. For example, all the children in a school may "know" who defaced a bathroom stall, even though none of them actually witnessed the act.
• A Witness's Character for Truthfulness or Untruthfulness. A witness's credibility may be attacked or supported through testimony regarding the witness's reputation for truthfulness or untruthfulness, or through opinion testimony concerning that character trait. Thus, in a world with truth spells, a witness might choose to submit to a truth spell to counter evidence suggesting that he or she is dishonest.
• Religious Beliefs or Opinions. Evidence of a witness's religious beliefs or opinions is generally not admissible to attack or support the witness's credibility. Thus, even if a witness were testifying truthfully about such matters, that testimony would ordinarily remain inadmissible for purposes of assessing credibility.
• Opinion Testimony from Lay Witnesses. A lay witness may not offer an opinion unless (1) it is based on the witness's personal knowledge, (2) it is helpful to understanding the witness's testimony or determining a fact in issue, and (3) it is not based on specialized or technical knowledge. For example, a witness testifies that a woman emerged from a bedroom carrying a bloody knife. A follow-up question might ask for an opinion: "How did she appear to you emotionally?" A clever witness under a truth spell might attempt to minimize or obscure the truth through careful word choice. If a truth spell extends to opinions and emotional impressions, however, it could reduce this problem.
• Expert Witnesses. This becomes a sticky wicket because most experts are hired because they are willing to offer a favorable opinion. But is the favorable opinion the expert's true belief? If experts were subjected to truth spells, a person might have a very hard time finding an expert willing to testify or offer an opinion on their behalf. I would imagine that most experts subject to a truth spell would offer only narrow and hyper specific opinions.
• Hearsay. This is a major issue in evidence law and is subject to numerous exceptions. The basic principle is that courts generally prefer testimony based on what a witness personally knows rather than what someone else told the witness. Most hearsay exceptions are grounded in common sense and concerns about reliability. For example, hearsay restrictions often do not apply in the same way to admissions by a party-opponent, certain official government records, newspaper reports admitted under specific exceptions, or regularly maintained business records such as sign-in sheets. You would have to decide whether a person's prior statements made under a truth spell qualify as an exception to the hearsay rule. In other words, could I testify about what I heard you say while under a truth spell because the spell provides an additional indication of reliability?

How Do Lawyers' Jobs Change?

If I were advising a person or business in this world, I would constantly counsel them to compartmentalize and silo decision-making in order to limit the scope of any future testimony. I would also be meticulous about protecting privileged communications. If every witness were subject to a truth spell, cross-examination would focus less on exposing dishonesty and more on resolving ambiguities and clarifying incomplete answers. Unfortunately, I suspect that if truth spells were real, witness examinations would often devolve into highly pedantic disputes over language and word choice. For example, a witness might truthfully testify that she saw a man "cut up" the victim. The obvious follow-up question would be: "Did the man cut Mr. Smith in the ordinary manner of a surgeon performing a medical procedure, or was he doing something outside the scope of legitimate medical treatment?" In a world governed by truth spells, precision in questioning would become just as important as honesty in answering.

In sum, I hope this helps you think through these issues.