Suppose a "Hollywood style" truth serum existed, whereby if a person is given the serum, that person is compelled to truthfully answer any question put to them.

The following facts are true in all of the scenarios:

  • Clyde Criminal commits a crime
  • Victoria Vigilante catches him in the act, injects him with truth serum, and leaves him for the police
  • Victoria Vigilante leaves, Officer Olivia arrives a few minutes later

Clyde's best bet is to exercise his right to remain silent until the serum wears off. But what would be the value to the prosecutor of Clyde's confession if he confessed under these various circumstances:

  1. Before Olivia speaks, Clyde confesses to the crime.
  2. After Olivia reads Clyde his Miranda warning, but without being asked any questions, Clyde confesses.
  3. After the Miranda warning, Olivia asks Clyde "What happened?". Clyde confesses.
  4. After the Miranda warning, Olivia asks Clyde "What happened?". Clyde says "I would prefer to remain silent, but I can't stop myself from telling you..." Clyde then confesses.
  5. Before Olivia arrives, Victoria questions Clyde and records his confession. Victoria then leaves Clyde and the recording for Olivia to find.

5 Answers 5


Miranda rights do not attach until the suspect is subject to custodial interrogation. "Custody" means that the suspect reasonably believes that he is not free to leave the conversation. "Interrogation" means that the officer is engaging in direct questioning or other conduct that would reasonably be expected to elicit a response.

A suspect is free to waive his Miranda rights and begin speaking without a lawyer, but a waiver must be knowing, intelligent and voluntary. "Voluntary" means that the waiver is obtained without coercion (torture, threats or promises) by the government.

None of the five scenarios indicate that Clyde ever believes he is in custody, so he has no Miranda rights in any of them, making his confession admissible in all of them. But to play it out further, let's assume that Officer Olivia arrives and immediately slaps handcuffs on Clyde:

  1. No interrogation, no Miranda rights. The confession is admissible.
  2. No interrogation, no Miranda rights. The confession is admissible.
  3. Miranda rights attached at the beginning of questioning. Clyde waived by confessing. Reading the Miranda rights established that the waiver was knowing. We don't have any facts suggesting the waiver was not intelligent. The waiver was not obtained by government coercion, so it was voluntary. The waiver was effective, so the confession is admissible.
  4. Same as 3.
  5. No interrogation, no Miranda rights. The confession is admissible.

The key thing to keep in mind here is that the purpose of the Fifth Amendment right against self-incrimination was to avoid misconduct by the government, and it has generally been implemented only to that end.

The key case here is Colorado v. Connelly, 479 U.S. 157 (1986), which involved a guy who approached a police officer and asked to talk about a murder he had committed. The officer Mirandized him, and he told them all about the murder and where he buried the body. It turned out that he was a chronic schizophrenic and was going through a psychotic break at the time of the confession, which he had only offered because "God's voice" told him to.

As with your truth serum scenario, the question became whether the Miranda waiver satisfied the voluntariness requirement. The Colorado Supreme Court held that "capacity for rational judgment and free choice may be overborne as much by certain forms of severe mental illness as by external pressure." But the U.S. Supreme Court reversed, holding that neither the defendant's due-process rights nor his right against self-incrimination are offended by non-governmental influences, even when they undercut the defendant's free will.

Since then, other courts have relied on Connelly to hold that voluntariness was not defeated by:

tl;dr: Because the truth serum was not administered by the government, the confession is admissible in all five scenarios.


Contrary to the other answers, we cannot be certain, although the odds favor admissibility. It is clearly established that as long as the government does not receive illegally-obtained evidence with dirty hands, the exclusionary rule does not apply: see Burdeau v. McDowell, 256 U.S. 465:

The Fourth Amendment gives protection against unlawful searches and seizures, and, as shown in the previous cases, its protection applies to governmental action

(That case was about stuff taken illegally by non-government individuals). The court also mentions the 5th Amendment, but does not specifically retrict the rule to confessions arising from non-governmental action:

The Fifth Amendment, as its terms import, is intended to secure the citizen from compulsory testimony against himself. It protects from extorted confessions, or examinations in court proceedings by compulsory methods.

Connelly involves the situation where a person is not "in his right mind", and related cases indicate that the exclusionary rule applies to confessions obtained when the defendant is tired, etc. But these cases do not involve compulsion.

A first test would be a gunpoint confession, where a non-government actor forced a person to confess -- would that be admissible? I don't know of any case that doesn't involve government agents having dirty hands. If it is decided that non-government gunpoint confessions are admissible (following Burdeau), it still has to be determined whether such a drug, or the Lasso of Hestia, would be found to be "compulsion".

Since the exclusionary rule is contracting, not expanding, it is likely that non-government gunpoint confessions will be allowed, but we don't know for sure.

  • 1
    Connelly answers this, and the answer is that it's admissible: "The most outrageous behavior by a private party seeking to secure evidence against a defendant does not make that evidence inadmissible under the Due Process Clause."
    – bdb484
    Jul 9, 2018 at 2:39

If such a "hollywood-style" truth drug existed and had been established to be reliable I am sure that there would be either new legislation or new court cases on just when and how it could be used, and when statements made under its influence would be admissible. But who knows what those would be. They probably would not be exactly the same as current case law.


Contrary to the other answer, there is a very strong defense: One, Victoria Vigilante is clearly guilty of assault and battery. Second, it is clear that Clyde Criminal isn't making a voluntary statement, but has been forced. Since he has been forced, having no choice but confessing to a crime, there must be serious doubt that he was actually forced to say the truth, and not just forced to confess a crime, independent of whether it was the truth or not.

  • 1
    I agree with all these assessments, but I don't think they answer the OP's question, which is about whether the confession would be admissible. Criminal acquisition of evidence and potential unreliability are grounds for a jury to doubt evidence, but they aren't grounds for exclusion.
    – bdb484
    Jul 8, 2018 at 18:45
  • On further review, I actually don't agree with the premise that "there must be serious doubt that he was actually forced to say the truth," as it is explicitly contrary to the facts provided.
    – bdb484
    Jul 12, 2018 at 8:14
  • If a Hollywood-style truth serum exists that forces people to tell the truth, then it is very reasonable that another serum exists that forces people to say whatever someone wants them to say.
    – gnasher729
    Jul 12, 2018 at 22:54
  • 1
    We're obviously into fantasy land here, but I don't see how the existence of a truth serum implies the existence of a mind-reading potion. Either way, that is not the serum that was administered.
    – bdb484
    Jul 12, 2018 at 23:06

Before Olivia speaks, Clyde confesses to the crime.

Admissible if and only if the nature of Truth Serum is unknown to the average cop. Your vigilante might not be known to police and thus, the criminal process will have to show evidence of the drugging to throw the confession (and any evidence discovered by the confession that would not have been found through course of the investigation).

After Olivia reads Clyde his Miranda warning, but without being asked any questions, Clyde confesses.

Probably No. I'm unsure of the admissibility of a confession before Miranda or given during the course of Miranda. If it is ordinarily admissible, see answer one. If not, see answer three. A good defense lawyer should be able to get answer one thrown out.

After the Miranda warning, Olivia asks Clyde "What happened?". Clyde confesses.

Trick Question, this scenario would be (likely) legally impossible. It's at this time we have to look at the content of the Miranda Warning. There is no prescribed statement, but they must include the following four facts:

  • they have the right to remain silent
    • anything the suspect does say can and may be used against them in a court of law
    • they have the right to have an attorney present before and during the questioning
    • they have the right, if they cannot afford the services of an attorney, to have one appointed, at public expense and without cost to them, to represent them before and during the questioning

The Police must also get the suspect to acknowledge that he understands his rights. This typically is phrased with the question of "Do you Understand these Rights as I have read them to you?" Clyde would answer yes here.

Because an improper Miranda rights administration could get potential statements by the suspect thrown out, most modern police follow up with one more question for the purposes of CYA: "Understanding these rights, do you wish to speak to me at this time?"

Clyde's truthful response to this question would be a "No." From here, it depends on both parties next actions. Olivia MAY stop talking to Clyde. But she doesn't have to stop talking with Clyde nearby. She can make up wild scenarios that likely are not true, as she has no evidence, to which Clyde could easily deny... it didn't happen like that (i.e. "I bet you killed him with a gun. You seem like a gun guy, don't you think?" "No, I protested the NRA last week". Clyde could explain he's under duress of Truth Serum and thus he would like to not talk to them, but he can't... this could get the chatty Olivia scenario out away from him. Clyde could answer "No and I want my lawyer!" At which point Olivia must stop talking to Clyde... any questioning without Lawyer Larry Esposito, Esq. (Two can play this alliterative name game) will be dismissed.

This also calls into question "What is Truthful?" Is Clyde compelled to speak only facts in both the spirit and the letter of the law? Or can he get away with the truth but still not say incriminating? For example, if I tell a friend that I think their new decor is a dream, when I hate it, did I tell a lie, or did I just not go in depth enough to fully explain? After all, Nightmares are dreams too?

But that's neither here nor there... the first two questions posed to Clyde would may stop the conversation in it's tracks, depending on how the police and Clyde respond. Clyde's best bet is to demand his lawyer, which will stop it.

After the Miranda warning, Olivia asks Clyde "What happened?". Clyde says "I would prefer to remain silent, but I can't stop myself from telling you..." Clyde then confesses.

Without any policy change, Clyde is what is called in the legal profession, screwed. The Confession will probably be valid enough to create sufficient evidence to see a judge. A good defense lawyer could get it thrown out... but that relies on proof that Clyde was drugged with truth serum. If it's well known to work, the admission should be enough for good cops to get jittery enough to back off until they get the stuff neutralized. Or at the least determine he is capable of answering of his own free will.

Before Olivia arrives, Victoria questions Clyde and records his confession. Victoria then leaves Clyde and the recording for Olivia to find.

Tricky and probably going to go down to proprietorial evidence. Victoria has committed a crime, as it is unlawful to forcibly drug someone in such a manor. While evidence of a separate (Clyde's Confession) crime gathered in the commission of a crime (Victoria's drugging of Clyde), there is going to be one hell of an appeals process over this. I doubt the confession would be presented in trial, and if it did, it would certainly be significant enough to rise to SCOTUS on appeals. At present make up of the Court, they tend to be highly favorable of defending the suspects rights, though at time of writing, there is a vacancy and this would not be heard until October 19 at the earliest (the Oct18 docket is largely decided). While a nominee has been named at time of writing he is not confirmed and we don't know how he will affect the court in this manner.

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