I see. It's possible to detect the scheme per se even though the detection would not lead to charges (ballots from the people registered at the same address are completely legal) and thus would not be conducted. The point your correspondent has initially made: it's impossible to detect illegal voting in such a scheme.
> even though the detection would not lead to charges
Didn't you cite a charging document upthread?
What...?
Virtually every type of fraud is first detected by detection of a nominally legal but abnormal behavior, then it's investigated to figure out whether fraud actually occurred. That would – obviously – be exactly how any voter fraud detection scheme works, but I guess you're saying that because the initially detected abnormality is not itself illegal, it wouldn't be investigated?
This is like saying "it's not illegal for all the numbers on your tax return to end in $xxxx.00 and $xxxx.50, so therefore tax fraud is undetectable by means of analyzing numerical patterns."