Question

the judge has already heard his statement.(use:what)

Answer 1

The judge has already heard what he told in his statement.

Answer 2

What is What?
What is the word which works as a determiners, pronoun or adverb.

1. Determiners:

◙ Asking for information specifying something.
Eg- What time is it?

◙ (Amount of something) whatever
Eg- He had been robbed of what little money he had.

2. Pronoun:

◙ Asking for information specifying something.
Eg- What is your name?

◙ Things to specify something:
Eg- What we need is a food and water.

3. Adverb:

◙ To what extent?
Eg- What does it matter?

◙ Used to indicate an estimate.
Eg- See you, what , about four?


Now the question is:
The judge has already heard his statement.(use:what)


So the answer is:
The judge has already heard what he told in his statement.