Suppose you're about to be attacked by a grizzly bear. There you are, enjoying nature and minding your own business when you spot the hairy beast lumbering toward you. You have exactly three slugs left in your shotgun, but you feel confident that two slugs would be enough. Do you save that last shot?
Of course not. Two may do it, but you won't know for sure until it's too late to change your mind, and the outcome of this encounter is going to be, ah, dispositive, one way or another.
What does this have to do with appeals? Everything. Appellate lawyers are forever going on about the need to trim your arguments down to the bone, to save overworked judges time and effort when reading your brief. Pick your best arguments, the mantra goes, and omit the rest.
That advice is sound — but like most things in the law, there's an exception. When you are the non-movant opposing a dispositive motion in the trial court, like a summary-judgment motion, you must include in your responsive brief every argument that you might want available to you on appeal, even if you think it unlikely that the motion will succeed and even if you think you can prevail using only one or two arguments.
Like grizzlies, trial judges are unpredictable creatures, and if your adversary's motion is granted and you appeal, you risk the appellate court deeming waived any argument that you didn’t make to the trial court in opposing the motion.
And note well: at least in some jurisdictions, you cannot preserve an argument for appeal by raising it for the first time in a postjudgment motion in the trial court. A trial judge has discretion to consider a postjudgment argument, but will not be reversed for failing to. See, e.g., Ex parte City of Montgomery, 758 So. 2d 565 (Ala. 1999).
It may not be a fair rule, since the movant can pick and choose their arguments, and if they lose the case simply goes on. But as the party opposing a dispositive motion, the downside potential for you is much higher if you omit potentially meritorious arguments simply to save space.
So if you think your two good arguments will suffice but have a third issue you could raise, remember that in this case, it is better to err on the side of inclusion.
By the time the judge rules, it may be too late to fire that last shot.