It is sometimes said that you cannot prove a negative. The bad news is that in law, one may on occasion be asked to do just that. The good news is that, sometimes, one can indeed prove a negative.
A typical example involves the post office. Courts will presume that a letter which was mailed was received. Someone claiming not to have received it must prove they did not. Some courts will take a statement under oath to that effect at face value. Florida’s do not, so the would-be recipient must, in essence, prove a negative, that the letter never made it to them.
Thankfully, it is sometimes possible to prove a negative, typically by showing circumstances incompatible with the positive proposition – here, incompatible with the proposition that the letter was received. If the recipient had been out of the country for a considerable amount of time, for instance, that would be inconsistent with receiving a letter sent to his states-side home. Multiple testimonies beside the recipient’s own may also do the trick. Likewise, there will be times when the recipient’s actions in the days and weeks that followed mailing are inconsistent with the conduct of someone who received the kind of letter sent.
In these cases, the onus will be on the attorney to know who needs to prove what and how – another example where attention to detail trumps razzle dazzle.