Interrogation can be either words or actions (designed to elicit an incriminating response). Note that (cf. Brewer) incorporation of facts that are specific to the defendant might make cop talk more interrogation-ish.
So why the differing outcome between here and Brewer? Can it possibly be that the degree of interrogation is the decisive factor? But you have a right not to be interrogated at all!
So here, it's not interrogation because there couldn't be a realistic expectation that the statements would produce an incriminating result. Some absurdity here: as long as the police think they are interrogating you with highly ineffective means, it's OK?
We have an objective focus on the behavior of the police, and a subjective focus on the mental state of the person in custody. The intent of the officers isn't important (because obviously they're trying to get incriminating statements), just the nature of their conduct.
One potentially helpful way of distinguishing the two is whether the cops might conceivably have had the conversation on their own, without the suspect present. In Innis, it's plausible, but far less so in Brewer. Or, from another angle, would prohibiting the utterance in question get us to a point where police are essentially prohibited from saying anything at all (which is obviously impractical)?
Maybe the holding here is that questioning after invocation is prohibited, and there will be times when non-explicit things will count as questioning. Innis himself loses, but in this light, it's kind of a defense-oriented case.
See footnote 5: by "incriminating response," we mean any statement that the prosecution is likely to want to use at trial (so exculpatory or inculpatory statements are both covered: i.e., falsely exculpatory statements that can be discredited at trial).
Practice tip: for every client, maybe get them to sign a document saying they invoke their right to counsel under 6A, and file it with the court and serve it on the prosecutor.
Interesting ethical
And these got expanded: at public expense, effective assistance.
But if the violation is already in the past, the evidence can be introduced for impeachment.
This is a softening of the stronger rule from Massiah.