English to Spanish Law/Patents Law: Contract(s) to the strict proof thereof

Hi,

I'm translating a statement of defence where the plaintiff claims that the defendant is responsible for causing him to fall on the floor of a resort, due too poor maintenance conditions. Here is the sentence I'm having trouble with: XXX specifically denies that the Plaintiff is entitled to the relief claimed in subsections (a) to (f) of the Statement of Claim, and puts the Plaintiff to the strict proof thereof. How do I translate "to the strict proof thereof"? Thanks a lot in advance!