Legal Question in Civil Litigation in California

You are up against both the Best Evidence Rule and the whole set of hearsay rules. The first thing you need is a witness to what is on your phone. The more neutral the better. Then you want that witness to be able to testify to how you got it off the phone. If you have a phone that can record screen shots, your best bet is to do that and then email them to the witness, have them print it out, and provide a declaration under penalty of perjury of every step that was taken.

None of the above.

Such messages, even if still on your phone, are likely to be admissible.

Enforceable contracts are documented by signed agreements, or at least credible and admissible documents evidencing all the terms of the claimed agreement.. You get to argue 'he said, she said', and 'your word against his' in court, supported by any other writings or witnesses you may or may not have.

If this is small claims court, good luck, give it a shot.

If this is a large amount requiring Superior Court lawsuit, you'd better at least consult with an attorney to see if there is any chance of prevailing, and if it makes sense for you to hire an attorney.

If serious about doing so, feel free to contact me.

California does not have the Best Evidence Rule any more. A statement and admission of a party opponent are both exceptions to the hearsay rule. To be admissible, the phone is usually brought to court, and presented to the judge for viewing of text messages. Testimony must be given that identifies the phone, the sender, and the recipient, and any other relevant information.