What would be the most natural way to express "Not since...have/has..."

I'm wondering how one would best translate the expression "Not since…have/has…" in Japanese.
For example a teacher saying, "Not since Mitsuya-kun was caught using a cheat sheet right in front of the teacher, have I seen such audacity in a student."
Would I say something like, "...してから…ことはない" ?
Maybe 三谷くんは白昼堂々カンニングぺーパーを使って捕まえてから、このよう猛々しい行為を見たことはない！
Would this sound at all natural to a native speaker?

The translation of "not since~" is correct, but 1) "to be caught" is passive, 2) I wouldn't use 白昼堂々 for "right in front of the teacher", 3) は rules the whole sentence, so if you use it after 三谷くん, 三谷くん is also interpreted as the subject of 見たことはない, 4) it doesn't have the meaning "in a student".

In conclusion, your translation means "Not since Mitsuya-kun caught someone using a cheat sheet in broad daylight, has he(= Mitsuya-kun) seen such audacity (in people in general)."
(Just for clarification, the subject of "using a cheat sheet" is Mitsuya-kun, not "someone". "A cheat sheet" is the means he used.)

1) "to be caught" is passive

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Yep...I just realized that I made a rookie mistake here by using 捕まえる instead of 捕まえられる or 捕まる.

2) I wouldn't use 白昼堂々 for "right in front of the teacher"

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Would you say something like 先生の目の前 ?

Also, would 猛々しい mean something like "audacity" in the sense of not even trying to hide one's wrongdoing?

(Interestingly, the principal at the school that I work at said something like this sentence [in English, though] in reference to students brazenly using cell phones to cheat in front of the teacher.)

tgruff said:

Yep...I just realized that I made a rookie mistake here by using 捕まえる instead of 捕まえられる or 捕まる.

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tgruff said:

Would you say something like 先生の目の前 ?

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Yes, that's exactly the phrase I would use.

tgruff said:

Also, would 猛々しい mean something like "audacity" in the sense of not even trying to hide one's wrongdoing?

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猛々しい is more likely brave/heroic. 図太い, 厚かましい or 大胆な would suit it.