In a recent S.C. Court of Appeals case, the court describes the process and standard for authenticating text messages and social media messages. Just like any writing, the proponent of the evidence will have to use SCRE 901 to show that the writing is what it claims to be (or more specifically, they show that the person they think wrote it, wrote it).
First, proving who sent the message is always important. Why? Because it will go to relevance (and maybe hearsay). If the State wants to introduce texts from the defendant, then those messages will likely be considered admission by party opponent (so non hearsay), and they will be relevant because what the defendant says will likely be relevant. If the messages were sent from another person (not the defendant), then they would need to be nonhearsay, not hearsay, or an exception to hearsay; and also, they would need to be relevant.
So how does one prove who sent the messages? Well that is not always easy because anyone can deny it and unless they are on video (or something else), then it will be hard to prove. But for authentication purposes, the bar is low. So the proponent needs to merely give some circumstantial evidence that person X was the one who sent the messages:
Even if the proponent has the circumstantial (or direct) evidence of who sent the messages, is it enough evidence? What is the standard? Because the relevancy of the text messages are dependent on another fact (who the sender is), then the court should use SCRE 104 to determine admissibility.
The United States Supreme Court has explained Rule 104:
The court simply examines all the evidence in the case and decides whether the jury could reasonably find the conditional fact...by a preponderance of the evidence.
Huddleston v. United States, 485 U.S. 681, 690, 108 S. Ct. 1496, 1501, 99 L. Ed. 2d 771 (1988)
And in this specific case, the court explained: