Can/Could: Question Mark for Ability, Period for Request
The Period
Rulebase Summary
When 'can' or 'could' is used to ask about physical ability or capacity, it is a genuine question and takes a question mark. When 'can' or 'could' is used to get someone to do something (as a polite request), it takes a period. When the meaning seems to be asking someone to do something, default to treating it as a polite request with a period. The witness's response can sometimes help determine which meaning was intended.
Examples
Q. Can you state your full name for the record?
Q. Can you state your full name for the record.
Polite request for action, not asking about ability.
Q. Can you read the text on that monitor from where you sit.
Q. Can you read the text on that monitor from where you sit?
Genuinely asking about the witness's ability — question mark.
Transcript Notes
This is a gray area. Sometimes the witness's response reveals the intent — if they answer with names or information, the question was likely a request (period). If they answer 'No, I cannot,' it was likely asking about ability (question mark). Some reporters feel it is never appropriate to look to intent and you should simply punctuate the words as spoken.
Style Guide References (1)
BGGP