Special CBI judge A K Singh pronounced the verdict against 38-year-old Koli while the quantum of sentence will be given on Thursday.
Deepali's case is the fourth out of a total of 16 cases filed by the CBI in connection with the rape and murder of children and a young woman whose skeletal remains were found in Nithari in 2006.
While Moninder Singh Pander and his domestic help Surinder Koli were held accused in the case initially, the CBI named Koli as the prime accused in the chargesheet, stating there was lack of evidence against Pander.
Koli was awarded death sentence by the special court in May this year for the rape and murder of teenager Rachna. He has also been held guilty of rape and murder of 14-year-old Rimpa Haldar and eight-year-old Aarti by the special court.
The mother of Deepali, who was missing since June 2006 and whose name was mentioned in the complaint lodged in December that year about the children missing from the area, had identified her daughter through her footwear and the DNA test conducted on her skeletal remains confirmed it.
A total of 19 cases were filed in connection with the rape and murder of children and a young woman in Nithari in 2006 and the CBI filed chargesheets in 16 cases. Three cases were closed without trial due to lack of evidence.