The causal character of singularities is often studied in relation to the
existence of naked singularities and the subsequent possible violation of the
cosmic censorship conjecture. Generally one constructs a model in the framework
of General Relativity described in some specific coordinates and finds an ad
hoc procedure to analyze the character of the singularity. In this article we
show that the causal character of the zero-areal-radius (R=0) singularity in
spherically symmetric models is related with some specific invariants. In this
way, if some assumptions are satisfied, one can ascertain the causal character
of the singularity algorithmically through the computation of these invariants
and, therefore, independently of the coordinates used in the model.Comment: A misprint corrected in Theor. 4.1 /Cor. 4.
