How to properly calculate the normal of a triangle in a mesh?

I want to get the normal of every triangle in a mesh. Therefore I used Vector3.Cross(b - a, c - a).normalized, where a, b and c are the vertices of a triangle. My project contains some bugs that might be related to this code. Is it possible that the resulting normals sometimes face inward instead of outward? In other words, how do I know if that normalized cross product is always the outwards facing normal?