Why do we use past tense?

[alexander]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #115 "Tense Agreement", question 4

The witness ......... everyone that he hadn't had anything to do with the crime.

(a) convinces
(b) is convincing
(c) convinced
(d) has convinced

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #115 "Tense Agreement", answer 4

The witness convinced everyone that he hadn't had anything to do with the crime.

Correct answer: (c) convinced

Your answer was: incorrect
The witness has convinced everyone that he hadn't had anything to do with the crime.
_________________________

why do we use past tense? we dont know when the action took place

alexander

[Yankee]

Hi Alexander

You need the simple past tense (convinced) here because of the past perfect (hadn't had) in the second half of the sentence.
The witness convinced everyone that he hadn't had anything to do with the crime.

If the second half of the sentence were in the simple past (didn't have), then you could use the present perfect (has convinced) .
The witness has convinced everyone that he didn't have anything to do with the crime.

Amy