Here, it was said that a text message is legally binding. But I am interesting in that what would happen when the sender says that the message was not sent by them. It is not a challenging problem to get any „forged“ text message (or e-mail) to the device. Will the court request an information about the message from the service provider? Do mobile operators even store the text of the messages (in the EU)? What would happen when the operator would not able to provide the information?

Imagine this situation:

  1. I sell something. The sender wants to buy that.

  2. I receive a text message (using SMS), sent to me using a mobile network operator. Let's say that it says that the sender wants to buy that 100 €. I aggree.

  3. I modify the text of the message in the device (without changing the length, sender information, timestamps, character encoding etc.). Now, the message says that the sender must pay 200 €.

  4. The sender receives the thing, pays 100 €. I use the message as a evidence of that the sender agreed to pay 200 €. The sender also tries to use the (original) message stored in sender's device as an evidence for that the price was 100 €.

How can it be proven (e.g. at the court) that one of the messages was actually sent by the sender? I can imagine that the mobile network operator would provide an information about the message, but what if the text was not stored by the operator?

  • Technically, it could be very different for SMS or E-Mail. The later can be forged much easier.
    – PMF
    Commented Jun 10, 2022 at 15:28
  • I would say that both are equally easy. Many phones or SMS apps allow importing and exporting all the messages. The import functionality can be used to add a custom message to the phone.
    – jiwopene
    Commented Jun 10, 2022 at 15:38
  • 4
    In the United States, at least -- and probably in the EU as well -- the easy answer is that each side will present whatever evidence it has and the court will decide who it believes. A well-advised client would hire a data-forensics expert to examine both phones to find evidence of tampering, but how they do that is probably a question better directed to another SE site.
    – bdb484
    Commented Jun 10, 2022 at 16:14
  • 1
    @bdb484: And of course, hiring a data-forensics expert over a difference of 100€ might not be cost-effective. Commented Jun 10, 2022 at 17:21
  • 1
    @PMF i think you are confusing spoofing and forgery. Yes, spoofing an email (making it show from someone other than the true sender, on a third party recipient's device) is much easier than spoofing a text. However, forging a message is different. This just requires the "recipient" to generate what appears identical to a message sent by the "sender," but not send it to someone else with this false impression. The copy on his computer may be inspected for authenticity, so it may need to pass that, but it does not need to be received on a third party's device with the false sender identity...
    – Someone
    Commented Jun 11, 2022 at 4:21

1 Answer 1


Each side presents the evidence that they wish and the court decides who to believe

This will involve lay witnesses who testify to what they saw and heard, expert witnesses who can give opinions and physical evidence.

The onus of proof lies on the plaintiff, the one seeking the extra money, so they have to prove their version. If the court gives more weight to their version, they win. If the give less weight or equal weight, they lose.

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