This work is based on the idea of analyzing the behavior all over the life-cycle of the source files having a high number of faults at their first release. In terms of predictability, our study helps to understand if files that are faulty in their first release tend to remain faulty in later releases, and investigates the ways to assure a higher reliability to the most faulty programs, testing them carefully or lowering the complexity of their structure. The purpose of this paper is to verify empirically our hypothesis, through an experimental analysis on two different projects, and to find causes observing the structure of the faulty files.As a conclusion, we can say that the number of faults at the first release of source files is an early and significant index of its expected defect rate and reliability.