The reason for the alphabetical order rule is that I can't know the order the player will find the evidence in. If I did, I could drop the system altogether.
Suppose, in a purely hypothetical example, that presenting the whippet puppy to Franziska von Karma causes her to drop her whip, which is covered in blood (evidence code: wh). Elsewhere, picking a lock nets you Maya Fey's Diary (evidence code ma), and using fingerprint powder on a doorknob gets you Chuck Norris's fingerprints (evidence code ch). That's only three pieces of evidence, and already there are 16 combinations to consider - since the player might not find all three pieces of evidence. On the other hand, if they have to enter the evidence they've found in alphabetical order, there are only 7 possibilities (ch, ma, wh, chma, chwh, mawh, chmawh), and at least some of those can be given the "You don't have enough evidence to bring this to court!" response.
I hope to use 'checkpoints' at several points during the investigation to keep this from getting overwhelming. For example, after exploring the Bistro crime scene, the player will be asked to demonstrate that they've found everything relevant by entering the compound code for all evidence they found at the Bistro. The evidence will then be added to the Court Record, and the compound code will be reset. Later, they'll have to give all of the evidence they have found since searching the Bistro crime scene. Then it will, again, be added to the Court Record, and the compound code reset once more. The player should never have to alphabetize ten codes at once.