Does a message on a phone prove who sent it?¶

No. It links a message artefact to a device, number, account or conversation; identifying the human author requires evidence of relevant-time control.

The apparent sender may be indirect¶

Devices and accounts can be shared, borrowed or remotely accessed. Messages may be scheduled, automated, restored or synchronised from another session. A local “sent” label records the application's state, not who typed the content.

Attribute device, session and person¶

Use message IDs, provider sessions, possession, unlock access, drafts, location, witnesses, CCTV and surrounding communications. Identify whether the action originated locally and who controlled the account and handset then. Contact display names remain unverified labels.