You meet with your lawyer and have them collect the evidence and if they feel the need, they will get forensics on such.
If it's gone and the subpoena fails, your lawyer is again the one to talk.
DO NOT FALL FOR THE SCAMMERS THAT POST RECOVERY SOFTWARE. You can find these on your own but so far these are outright failures and scams that prey on folk like you.
RECOVERED TEXTS are rarely acceptable in court. A good lawyer will get them thrown out. My advice is to stop and head back to your lawyer.
Hi,
I am in the middle of a custody battle with my ex-partner who was and is extremely pathological and abusive and now a 2x sex offender. There is a police investigation going on but without a confession, the case is weak. I have an iPhone that syncs with my messages on ichat on my Mac desktop. He came into my house and deleted them. Apple support and Sprint were not able to help. However, by reading forums, I ended up finding fragments of the conversations and the evidence I needed, by going through the systems library, and archives and by simply typing his name and ichat transcript, and it all came back- EXCEPT for the month of May and those are the ones I need the most. What I have unfortunately, is not enough and the proof lies in May. I have other ichat transcripts from other people in May, so I don't know how he did it and why his are missing, and if it is even possible to recover.
My Time Machine was never set up, my iphone backups do not have the month of May- I do not trust the recovery software programs, they are pricey and I don't want to pay x amount of dollars if they won't help. Sprint said you could subpoena however, when my attorney tried, they were unable to- I can only get the dates and times- not the content. Someone at Sprint told me they were 99.9% sure you can subpoena, but only the judge can, but our hearing is not set for weeks to come and if I can find this now, I will have what I need to file an emergency motion.
I tried restoring my iPhone, to one of the old back ups, which was unsuccessful. I have read so many forums. Spotlight, iCloud- unsuccessful- Apple Support tried. I need to recover the messages between he and I, which transpired in the month of May in order to acquire the proof/hard evidence I need for this case. If you think you can help and have any advice to offer on how I can recover the messages I need, my child and I would be in your debt. Thank you.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic