Alternatives need a connection to the file
A useful alternative explains the same observation through a different supported mechanism. It is not an unlimited list of things that could conceivably happen. If a name appears after its owner's death, consider a documented reassignment or later filing before inventing impersonation. Keep the alternatives few enough that you can identify what evidence would distinguish them.
Worked example: the late signature
A form filed in March bears the signature of someone who died in January. One explanation is later misuse of the signature. Another is that the form was signed earlier and filed after a delay. A December dispatch entry linked to that exact form would favor the second explanation. Merely knowing that delays sometimes happen would not be enough to establish it.
Compare predictions
For each alternative, write one observation you would expect if it were true and one that would count against it. Then return to the supplied records. In Somatry, this keeps a theory flexible without making it vague. You are not required to believe every alternative equally. You are making the basis for preferring one visible, so the conclusion follows from the case rather than from your attachment to a compelling first impression.