Tenant create forged rental agreement for injunction to eviction order

I gave my property for tenancy in June 2012 with oral agreement for 2 years and then continued by a written agreement in 2015 for 11 months. After the expiry of the tenancy period, I asked him to vacate. But, some unknown persons claimed possession from June, 2012 itself and obtained injection to vacate by forging a rental agreement (dated June,2012) for 12 years with Rs.10.00 lakhs as advance. My tenant is one of the witnesses in the forged rental agreement. My tenant continues to possess my property under the cover of injection for the forged rental agreement and doing the business without paying rent for more than 18 months. Apart from contesting the injunction suit, I filed the eviction suit also, which are in progress. My queries are: As per the law, who is in possession of my property? --- The fake tenant or the real tenant? Of course, both have colluded to demand money. Is it mandatory for the judge to obtain the opinion of Forensic science expert before delivering justice?