under penalty of perjury

I cannot find a Tagalog equivalent for "perjury" - legal matters and rulings in the Philippines always seem to be conducted in English!

4 +1	sa ilalim ng kaparusahan ng panunumpa na walang katotohanan (perjury)	Leny Vargas
4	sa ilalim ng batas na may kaparusahan ukol sa panunumpa na pawang kasinungalingan lamang.	Judy Almodovar

Proposed translations

France

CPR (Conscientious, Punctual & Reliable)

Native in: Tagalog , English

Works in: English to Tagalog, Tagalog to English, French to Tagalog, and 5 more.

sa ilalim ng kaparusahan ng panunumpa na walang katotohanan (perjury)

perjury - panunumpa ng walang katotohanan

Indeed perjury is the legal term and is very common. But it is important that other Filipinos (those who do not understand what perjury is) understand what it means. Therefore I suggest you translate it.

"sa ilalim ng kaparusahan ng panunumpa na walang katotohanan o perjury"

For me 'na' is acceptable. but true that nang is more common. Dante's suggestion of 'nang' is fine.