During the trial, the expert was called to testify about the forensic evidence.

testify 是动词，由词根 testi-（与"见证"相关）和后缀 -fy（表示"使成为"或"做"的动作）组成，字面意思是"作见证"。在法律语境中特指"作证"，即在法庭上提供证言或证据。