I'm using Secure and Accessible PHP Contact Form v.2.1WP on my WP site. The FAQ says: Is the Anti-Spam question or its answer case-sensitive? No. Both question and answer are case-insensitive to admin and user.
However, I find that to not be the case. The following are my anti-spam question and answer:
Your anti-spam question is Is fire hot or cold?.
Your anti-spam answer is hot.
"hot" works, but "Hot" does not. "Hot" produces this message:
Results: Sorry, there was an error.
Anti-Spam Question/Answer Mismatch
Give it a try if you want: