Explanation:

- The law of evidence is a part of procedural law, which governs the proof of facts in legal proceedings.

- Option 1: This relates to determining if a witness is competent to testify, which is a procedural aspect.

- Option 2: This involves deciding if something needs to be proven by written evidence, which is a procedural decision on how evidence should be presented.

- Option 3: This pertains to assessing whether certain evidence proves a fact, also a procedural consideration.

- Option 4: All of the above are aspects of the procedure under the law of evidence.

Answer: Option 4 - All of the above