One mistake. What should be the price of one mistake? To some extent, the answer to those questions for lawyers and lawyer discipline matters ought to be foreordained in two consecutive paragraphs of the Scope portion of the ABA Model Rules:
 ….the rules presuppose that whether or not discipline should be imposed for a violation … depend on all the circumstances, such as the willfulness and seriousness of the violation….
 Violation of a Rule should not itself give rise to a cause of action against a lawyer nor should it create any presumption in such a case that a legal duty has been breached. In addition, violation of a Rule does not necessarily warrant any other nondisciplinary remedy …. Nevertheless, since the Rules do establish standards of conduct by lawyers, a lawyer’s violation of a Rule may be evidence of breach of the applicable standard of conduct.
Most folks who practice in any area where the ethics rules and substantive causes of action may intersect, such as legal malpractice matters, are quite familiar with their state’s version of the language above from  that attempts to navigate a thorny path between what the standard of care requires of a lawyer versus what it takes to commit an ethical violation. The language I’ve excerpted in  is, I think, less commonly thought of but is highly important as it indicates an acknowledgement in the ethics rules themselves that conduct can both simultaneously amount to an ethical violation but be of such a low-level nature as to warrant no discipline whatsoever.
For what it is worth, I tend to think that the principle acknowledged in  is even more supportable by common sense than the path threaded by the language in  is.
An area where all of these concepts intertwine, and that serves as an easy -to-digest example, is an instance in which a lawyer makes a solitary mistake that can also be argued to violate an ethics rule. Pick your favorite poison, whether it is the missing of a statute of limitations or other deadline for a client or . . . actually those two tend to be the most readily explainable and the most likely to involve facts that also generate litigation over the error. Assuming that the affected client can satisfy the relevant jurisdiction’s case-within-a-case elements of proof, then the error will likely be actionable as a claim for legal malpractice. Such an error can also be viewed through the lens of the ethics rules as being in violation of RPC 1.1 – not providing competent representation to the affected client — or RPC 1.3 — not acting with reasonable diligence and promptness for the client — or both. Yet, even if viewed through that lens, it wouldn’t be unusual for such a matter to be addressed and remedied only through civil litigation or a settlement and not through the pursuit of any disciplinary proceedings.
Related to these thoughts, or at least explanatory of why they would result in the creation of a post, is the fact that California has now taken the long-awaited action of rolling out proposed revisions to its ethics rules that would replace its existing lawyer ethics rules with a set of rules that look more like the ABA Model Rules. If you want to go read the entirety of the proposed rules, you can go get them at this link. The public comment deadline on the California proposal is September 27, 2016.
There are a lot of interesting aspects of what California has proposed to adopt (as well as some of the rules they expressly have rejected adopting), and with any luck I’ll manage to dedicate at least one more post on the topic at a later time, but for today the point is to note that California as to proposed versions of Rule 1.1 and 1.3 offer up deviations from the ABA Model Rule language that are quite pertinent to the thought exercise about what should be the price of one mistake.
In both of proposed Rules 1.1 and 1.3, California would have the language of its rules read to rule out the idea that one instance of simple negligence could be an ethical violation of those rules at all. As proposed, California’s 1.1(a) would read:
A lawyer shall not intentionally, recklessly, with gross negligence, or repeatedly fail to perform legal services with competence.
Likewise, proposed Rule 1.3(a) would read:
A lawyer shall not intentionally, recklessly, with gross negligence, or repeatedly fail to act with reasonable diligence in representing a client.
If you’re writing on a clean slate, that sure seems like a good way to address these issues.