When a party petitions the Supreme Court for review, non-parties can submit letters to the court in support of review. (Rule 8.500(g).) Those letters can be effective. (See here and here).
The rules specify when a petition must be filed, but there is no fixed deadline for a supporting letter. We usually advise getting the letter on file before the court’s staff starts work on the conference memo regarding the petition, a time we used to estimate to be around 20 days after the petition’s filing, which is when the answer to the petition is due. That’s probably still good advice, but we now understand that taking a bit longer on the letter — even up to five weeks after the petition is filed — might not hurt.
Our current understanding is that, when a petition is filed, the case is assigned to an initial conference that will occur about five weeks later. (The court conferences on petitions for review most Wednesdays.) However, a petition is often not submitted at the initial conference to which it is assigned, but is continued to a later conference, usually for logistical reasons that are unrelated to the significance or merits of the issue presented. (Occasionally, a justice will have a petition continued after she or he reads the conference memo (see next paragraph), but the more common reason for a continuance is that there are older petitions that have to be considered first.)
Court central staff prepares conference memos for each petition. Those memos are typically distributed to the justices and their staffs about a week before the conference at which the petition will be considered. Central staff will typically start work on the conference memo about a week before that.
The critical factor about when work will start on a conference memo — our rule-of-thumb deadline for submitting a letter in support of review — thus seems to be whether the petition for review will be continued to a later conference. But, because the logistical reasons for a possible continuance are unknowable outside the court, three weeks after the petition for review is filed appears to still be the safest target date.
We are also informed that even last-minute supporting letters are considered, generally causing preparation of a supplemental conference memo, but we don’t recommend waiting until the last minute. We would rather have our client’s supporting letter — or letters by others supporting our client’s petition for review — in the central staff attorney’s hands before that attorney is working on the conference memo.
Finally, don’t be concerned if, whenever supporting letters are submitted, they don’t appear on the court’s online docket. They just don’t.