1. Nobody is going to do mass spectrometry in your case,
2. It will not go that far,
3. Writing acheque leaving the amount blank is not illegal. So, you will not get any legal advantage therefrom,
4. The moot point in this matter is that the other person shall have to prove the dischargeable liability of your relative on him for which he has allegedly issued the said cheque,
5. If he can not prove the dischargeable liability to that high level, it will naturaly come to the light that the amount space in the cheque was kept blank for him to fill up with properly calculated interest at bank rate which he has misused and put an exorbitant figure,
6. The said will then be termed as security cheque by the defending lawyer taking the case out of the purview of section 138 of N.I.Act.