It is open source? And will justice will depend on the device?
I seem to remember that red light camera tickets being contested on the grounds that as the software in the particular gatso camera was not available to be viewed by the court (it wasn't open source and the company wasn't willing to share the source with the court) then the conviction couldn't stand as it violated the principle that "the defendant and the court needs to be able to see the method by upon which the accusation is based".*
If the devices in our possession are used by and against us in legal proceedings, it surely won't be long before scrutiny of the very device itself becomes key to the verdict. Can't imagine Apple being too keen to provide its source code to comply with a court supoena to validate the evidence that is being attempted to be extracted from its watch in a low level civil action.
* - Florida seems to spring to mind and I don't know if the defence was successful.