Competence, Legal Malpractice, and Liability to Third Parties
The competence standard
Rule 1.1 requires legal knowledge, skill, thoroughness, and preparation reasonably necessary for the representation - not perfection or specialization. A general practitioner may accept an unfamiliar matter by studying the law or associating experienced counsel. Rules 1.3 (diligence) and 1.4 (communication) supply companion duties.
Malpractice
Legal malpractice is a civil claim; a disciplinary violation is a separate matter. Malpractice requires duty, breach, actual and proximate causation, and damages. The client must show that but for the error the outcome would have been better - in litigation, a "case within a case" proving the underlying claim would have succeeded and produced a collectible judgment. Expert testimony is generally required to establish the standard of care, unless the error is plain enough for lay jurors to recognize.
Liability to nonclients
Absent privity, a nonclient may recover for fraud or negligent misrepresentation when the lawyer supplies information for the guidance of others in their business transactions and the plaintiff justifiably relies (Restatement 552). Classic fact patterns: opinion letters, title work, and estate plans that fail the intended beneficiary. Rule 4.1 bars false statements of material fact or law to third persons, and Rule 8.4(c) bars dishonesty - discipline needs no damages, while civil liability does.
Traps
Equating negligence with discipline (discipline normally requires gross negligence, recklessness, or intentional misconduct); ignoring reliance as an element; assuming a lawyer is answerable to every person her work touches. Rule 1.8(h) permits limiting prospective malpractice liability only if the client is independently represented.
Rule of thumb
For any malpractice fact pattern, ask: what was the duty, what did the lawyer do, would the outcome have differed, and who was entitled to rely?