I am here to find out the what exactly step take in order to invalidate a patent. I went through many of the articles but I got confused , is it ok to cite the family patent in invalidation if the inventor is same but the assignee is different? what should we actually look in patent in order to invalidate a patent/ please answer this question in brief/...
The first step would be to sue the patent holder. Once the patent has been granted, it's a matter for the courts.
I don't have any examples of defensive suits launched prior to release of an infringing product, but it may occur.
Than main thing is that intellectual property litigation is considered ruinously expensive for all but the largest companies. The cases drag on for years and typically cost millions of dollars, with no certainty regarding outcome. (This is the reason "patent trolling" was so successful--most targets chose settlement, regarding it as the surest, most cost-effective solution.)