One of the key challenges of a traitor tracing scheme is to deal with the real scenarios. In this context, the tracing operation is usually constrained by the lack of information about the number of colluders and even the collusion channel. Indeed, the Tardos decoding is invariant regardless the type of collusion, which can be considered as a suboptimality of its accusation performance. In this paper, we propose to use a MAP-based estimation strategy which improves the Tardos decoding step and guarantees a good estimation results. Compared to the original version of Tardos code and the original MAP decoder operating in blind tracing scheme, the proposed technique takes the advantage of operating in hierarchical context to provide a more concise and accurate accusation decision, this in a short time.