CM/ECF (The Electronic Filing System used by federal courts) has a section for "amended motions". What are the circumstances under which a party could amend a motion? In federal court, can one amend a motion without leave if the other party has not yet responded?
What are the circumstances under which a party could amend a motion?
When circumstances have changed, since filing of the motion, in a way that leaving the motion uncorrected or outdated may lead to confusion or cause a "waste of judicial resources", respectively.
For instance, suppose A denounces in his motion that B has not responded to a subpoena for records. Immediately after filing the motion, B submits essentially trash to pretend he ultimately complied with the subpoena. In that case, A should amend his motion to update state of affairs: that B only produced trash. Doing so will preclude B's misleading allegation that "the motion should be denied as moot because B has already responded to the subpoena". Now A may want the court to scrutinize more in detail B's pseudo-response and, accordingly, pursue additional or different relief.
Another situation that warrants an amendment is where the moving party made a mistake that renders the substance or purpose of his motion confusing. Not doing so affords B the opportunity to defeat the motion merely by disproving A's inaccuracies.
can one amend a motion without leave if the other party has not yet responded?
I am not much knowledgeable of FRCP, but my "educated guess" is in the affirmative except for some specific types of motions or on belatedness of the amendment.
In fact, it sounds wasteful to call the court's attention regarding an obsolete motion on which the opposing party might not have even spent any effort yet. I doubt that FRCP are more stringent than states' procedural law in this regard.
That being said, see here for an example of ruling on a motion for leave to amend [motion for relief from order].
A need for leave seemingly derives from belatedness [of the motion to amend] or stems from the nature of the underlying motion, not from the mere necessity to make the amendment. See FRCP 60(a) and Notes of Advisory Committee on Rules -1946 Amendment:
after an appeal has been docketed in the appellate court and while it is pending, such a mistake may be corrected only with the appellate court's leave
a motion for new trial on the ground of newly discovered evidence is permitted within ten days after the entry of the judgment, or after that time upon leave of the court