Senior Eagle,
I know a few pilots who were caught legally drunk both Indians and Expats. Being son of a DGCA officer has nothing to do with still flying for an airline. The rules were same for everyone, first offence and you are grounded for three months without pay (during this time you were also advised to go for some form of counselling). Second offence and you were out. It is a DGCA regulation and all +ve tests were required to be reported to DGCA. The doctors could not fudge the results as they were required to print all the tests and report any positive.
When I was flying for KFA we had random breathalyser testing, at IndiGo we had 100% BA. Most airlines in India do random testing whereas IndiGo is 100% for both flight and cabin crew.
When flying for airline in USA I was never tested. Although, in USA they also check your urine/blood sample for drugs. Now if that was to be done in India (testing for drugs) it will open another big can of worms.