This paper presents a rigorous offline double fault diagnosis as well as a detection technique for Digital Microfluidic Biochips (DMFBs). Due to the underlying mixed technology biochips exhibit unique failure mechanisms and defects. Thus, offline and online test mechanisms are required to certify the dependability of the system. In this paper, the proposed algorithm detects double faults anywhere in the chip satisfying the dynamic fluidic constraints and improves the fault diagnosis time to an extent.