This is a good question, and because it involves court paperwork, warrants a better explanation.
When you have emails in an iCloud email account they are on iCloud.com and any devices signed into the AppleID.
If you delete emails they go into trash. If you empty trash, or have settings that automatically empty trash, then we need to go to recovery options.
If you're using Time Machine, you might be able to recover them this way. You'll want to have the Mail program open, Open Time machine from a Spotlight Search, and you will be able to go back in Time, and recover the missing Mail.
Use Time Machine to back up or restore your Mac - Apple Support
If you weren't using Time Machine, or are having trouble using it, you'll need to call Applecare 1-800-275-2273
Provide them with the serial number of your product, and the email for your AppleID
You'll need to ask for a senior advisor. They will review the Time Machine aspect and help you that way if they can. The other option is for them to 'unexpunge' the missing emails, or to escalate your AppleID/email account to engineering, to attempt to recover them.
The sooner the better. With data loss it is VITAL that you move quickly. Good luck!