The judgment that I cited earlier is also in respect of a special law. The general principle is the same, i.e., whether the investigation is done by a police officer who is lower in rank than the police officer who is authorized under law. The above case from Supreme Court is on the same issue.
As I mentioned earlier, the investigation is illegal in such case, but the illegality in investigation may not vitiate the proceedings unless miscarriage of justice is shown. Chances of acquittal or discharge in such case would thus depend on showing the miscarriage of justice (and to some extent, also, on whether such defect was pointed out at the initial stage).
As I mentioned, if you show this defect at the initial stage, the court may order a re-investigation by a competent officer, but chances of complete discharge or acquittal would be very limited, unless miscarriage of justice is shown.
You should engage some good lawyer who can properly guide in this regard in detail, especially with regard to the above legal principle.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.