Prospective clients frequently ask me if I guarantee results. I do not. I get paid for the work that I do, and I do the same quality work for my clients whether we win or lose, and whether we get a good deal or a bad deal.
There are lawyers out there who do "guarantee" results. For example, in Syracuse the firm Sommer & Sommer (website is trafficticketdwi -dot- com) says on their website in bold red: "you will not pay a fee unless we reduce your points and acheive [sic] our goals."
Yes, they do have the word "achieve" misspelled on their site. More important, they offer a guarantee. The problem is that this is effectively a contingent fee arrangement (payment of the fee is contingent on achieving a certain result), and contingent fees are generally prohibited (DR 5-103(A)(2)) and are specifically prohibited in criminal cases (DR 2-106(C)(1)). And while one might argue regarding DR 2-106 that traffic cases are not criminal, the listing of things this covers on their firm site includes "Driving on Suspended License," "Suspended Registration" and "No Insurance," all of which are misdemeanors in New York. For those who don't know, misdemeanors are crimes.
There are some fundamental ethical problems with an attorney making this kind of guarantee. Suppose you're in Court and are offered a deal for your client. The deal is not good enough to satisfy your guarantee, but is better than the likely outcome. The attorney may be inclined to do a trial against the client's interest in order to have some chance of getting a fee. While few attorneys really think this way in the middle of handling a case, we are supposed to avoid creating this kind of conflict in our work.
Another problem is the perception this may create that we have the power to make guarantees. People may think we have inside connections with prosecutors and courts. Perhaps that is true for some lawyers, but that is not something one should advertise. It creates an appearance of impropriety.
There are other problems with it, I'm sure, but my brain is dead today from lack of sleep, so you're all on your own to figure out the other issues. :-)