Modaux anglais : certitude, déduction et regret au passé

Rewrite the following scenarios using the correct modal verb structures to convey the intended nuance of certainty, deduction, or criticism regarding the past.

1. It is logically certain that the suspects escaped through the back window because there are footprints in the mud. (The suspects ______)
2. It was clearly a poor decision for the firm to ignore the market warning last year, which led to their bankruptcy. (The firm ______)
3. Given the lack of concrete evidence, it is possible, though not certain, that the system crash was caused by a malicious virus. (The system crash ______)
4. Analyze the logical deduction based on the evidence rate $R$. If the evidence threshold for a positive conclusion is $R > 0.85$, and we have observed $R = \frac{18}{20}$, apply the correct modal structure to express the degree of certainty regarding the system failure.