A matrix A whose entries come from the set {+, -, 0} is called a sign pattern matrix, or sign pattern. If A is a sign pattern and A is a real matrix for which each entry has the same sign as the corresponding entry of A, then A is said to be a realization of A. A sign pattern is said to be potentially nilpotent if it has a nilpotent realization. In this paper, a class of sign patterns, denoted by FSP(3, n-3), is introduced. The authors determine all potentially nilpotent sign patterns in FSP(3, 4), and prove that no sign pattern of even order in FSP(3, n-3) is potentially nilpotent.