When does a warning not to talk to the police become "witness tampering"?

Question

Every competent criminal defense attorney will advise their client (or anyone else) NEVER to talk to the police. Law professor James Duane gave a 45-minute lecture on this exact subject. So, obviously if a person with a cop at their door calls up Duane and asks him, "There is a cop at the door and he wants to ask me some questions." Professor Duane would obviously tell the person, "Under no circumstances should you say anything to the police." It would seem unlikely that Duane would be prosecuted for witness tampering.

However, let's imagine that the same person does not call Professor Duane, but calls their brother. Can the brother be charged with witness tampering?

At what point does advising a person not to talk to the police become "witness tampering"?

Answer 1

This question and many related ones are analysed in detail by Eugene Volokh, in a long paper that is worth reading in its entirety if you are interested in the topic.

The [Supreme] Court has offered “speech integral to [illegal] conduct” as one of the “well-defined and narrowly limited classes of speech” excluded from First Amendment protection. But if this exception is indeed to be well defined and narrowly limited, courts need to explain and cabin its scope. This Article — the first, to my knowledge, to consider the exception in depth — aims to help with that task.

On threats, he says:

Companies are generally barred from firing employees for voting for a union, and unions are generally barred from retaliating against employees for their speech. The Court therefore concluded that speech that threatens unlawful retaliation is itself unlawful.

On blackmail, he says:

[...] telling black citizens “stop shopping at white-owned stores or we’ll publicize your behavior to your neighbors and fellow church members” is similarly constitutionally protected. On the other hand, “vote for this civil rights bill or I’ll disclose that you cheated on your wife” is likely unprotected.

In general the line where the First Amendment protections end and criminal speech begins is surprisingly vague. General advice to avoid self-incrimination by not answering questions from the police is clearly protected. Threatening a witness with violence is clearly not. In between are shades of grey.

Answer 2

At what point does advising a person not to talk to the police become "witness tampering"?

When the brother's advice includes actual or threatened physical force.

Witness tampering is defined by 18 U.S. Code § 1512 to include:

(2) Whoever uses physical force or the threat of physical force against any person, or attempts to do so, with intent to —

...

• (C) hinder, delay, or prevent the communication to a law enforcement officer...

...

shall be punished as provided [below]

Answer 3

A conviction for witness tampering generally requires something more than simply giving advice.

Under federal law, witness tampering requires the use or threat of force to prevent a witness from cooperating with the police. Pure advice against cooperating cannot be a crime.

Under New York law, a conviction requires that the defendant induces the witness to dodge testifying or engages in some kind of deceit designed to affect the witness's testimony.

The broadest witness-tampering statute I'm aware of is California's, which prohibits both "knowingly and maliciously" dissuading a witness from attending or testifying at a trial, and dissuading a witness from reporting a crime or seeking charges based on that crime. I'm not familiar with how the courts have interpreted this law, but it seems to raise some serious First Amendment problems.