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.