What does "as" add to the sentence below?
The truthfulness of the declaration on this matter must be assessed only as at the time when it was made.
I think that if the "as" were omitted one would be obliged to make one's assessment of the truthfulness of the declaration at the time the declaration was made, and not postpone the assessment.
The "as" permits the assessment to be done later, but truthfulness has to be measured against facts and circumstances as they were when the declaration was made, not as they may have subsequently become. In other words "as at" is equivalent to "as it was at".
"The truthfulness of the declaration must be assessed only as it was at the time when it was made."
In other words, if the declaration changes after being made, this will not affect the assessment of the declaration since only its initial version may be assessed.
"must be assessed" and "should have been assessed" mean different things.