By "negative" malpractice, I mean sins of omission, such as missing a deadline, or omitting a key document from a filing.
By "positive" malpractice, I mean a sin of commission, such as misrepresenting information or manufacturing evidence.
IS one type of malpractice more serious than the other and more likely to draw sanctions because it is "willful?" Is the first type of error more likely to be fixable?
The question entangles two concepts that are not identical.
The standard of recovery for malpractice is negligence. Negligence could involve omissions. But, it could also involve positive acts, for example, introducing evidence or asking a question at trial or making an objection that is unintentionally harmful to the client that a reasonably competent attorney would not have done.
Intentional conduct can give rise to claims for punitive damages in what would otherwise be a pure negligence claim. But intentional conduct can involve omissions as well as commissions, such as intentionally not introducing evidence in the possession of an attorney that would exonerate a client because the attorney is annoyed with the client.
In addition to malpractice liability to a client, lawyers face potential sanctions from a court for misconduct, potential ethical sanctions implicating the lawyer's license, and civil actions for breach of fiduciary duty (e.g. in a conflict of interest case) that can result in forfeiture of fees. These kinds of non-malpractice consequences can also arise from both acts and from omissions. They are more likely to involve intentional conduct, but this isn't necessarily the case. Mismanagement of a trust account can result in serious sanctions in the absence of intentional conduct, and it isn't that hard to back into a conflict of interest either.
I don't know of any jurisdiction in the United States that recognizes any difference between the two. It's not a particularly useful distinction, largely because the range of potential malpractice or misconduct is so wide.
A lawyer arguably commits misconduct with a sin of commission both when he solicits an appreciative client (resulting in no discernible harm to anyone) and when he manufactures evidence (resulting in his client losing his case and being forced to pay millions of dollars in sanctions).
And a lawyer arguably commits misconduct with a sin of omission both when he fails to sufficiently research some aspect of the law governing his client's case (resulting in no discernible harm to anyone), and when he fails to obey a court order (resulting in his client losing his case and being forced to pay millions of dollars in sanctions).
Regardless of whether the misconduct is active or passive, there could be either no meaningful injury to anyone, or someone could be massively prejudiced. The courts are therefore more likely to inquire into the harm inflicted than into whether the injury was the result of active or passive misconduct.
Even "willfulness" is not always relevant. For instance, a lawyer who commingles client funds and personal funds should expect to be at risk for major sanctions, regardless of whether he did it with noble intentions or even completely accidentally.
