A: These are very good questions. We’ve all seen irrelevant and hearsay evidence offered and admitted without objection. Many of us have also seen attempts to offer inadmissible evidence in order to improperly taint or influence a trial. The line between these two things is often one of intention or purpose, which is perhaps why the cases and disciplinary decisions on this point are so few. Model Rule 3.4(e) addresses the issue: “A lawyer shall not…in trial, allude to any matter that the lawyer does not reasonably believe is relevant or that will not be supported by admissible evidence.” The key here is for the lawyer to have a reasonable belief about the offer, based on a legitimate argument that there is a basis for the relevance of the evidence, or an argument that it is either not hearsay or admissible under any one of the many exceptions to the hearsay rule. If the lawyer does not have (and cannot articulate) a basis for a reasonable belief of admissibility, then the lawyer fails the test of Rule 3.4(e) and should not offer the evidence. I note that in your first question you refer to the purpose of offering the “not directly relevant” evidence as being to show the opposing party as a “scumbag.” That, without more, would not be a proper basis for offering the evidence.
The question about hearsay evidence may also depend in part upon the treatment of hearsay in the relevant jurisdiction. Is it admissible if not objected to, even if it has little or no probative value? If so, then you could proceed without running afoul of Rule 3.4(e). Under Federal Rule of Evidence 802, “[h]earsay is not admissible” unless it falls within an exception of those rules or other law. Thus, if you could not “reasonably believe” it to be admissible under an exception, Rule 3.4(e)’s proscription would still apply.