Section 90 IPC specifies when consent is NOT valid: (1) given under fear of injury or misconception of fact, (2) given by a person of unsound mind or intoxicated, (3) given by a person under 12 years of age (unless contrary appears from context). The section protects vulnerable persons from exploitation through technically obtained but meaningless 'consent.'

1. 1 Pick up IPC.
2. 2 Go to Section 90.
3. 3 Read the conditions that invalidate consent: fear of injury, misconception of fact, unsound mind, intoxication, under-12 age.