verb
testify
TES-tih-fy/ˈtestɪfaɪ/
To give evidence that something is true, especially in a formal statement.
The witness testifies under oath about what she saw.

Etymology
The pieces express the act of bearing witness: making something known to others who do not know it firsthand. Giving evidence in court is a formal application of that idea.
In context
does context. Some parts of that call might include secondhand information, something the caller was told rather than saw directly. And in court, that's a line that matters. You can't testify to someone else's words unless a very specific exception
More examples
- He testified that the driver ran a red light.
- Several nurses are testifying before the committee today.
- These worn steps testify to years of heavy use.
Forms
testify · testifies · testified · testifying
testimony noun — A formal statement given as evidence.