This answer begins from the premise that we all have spirit within us. We are spiritual beings in a physical body first and foremost. This spirit is referred to by several different names, each having slightly different connotations depending on who’s using it. Common terms include; the soul, energy, God within, apparition, essence, life force, to name a few.
Having said this, then yes, your friend does have a spirit attached or within him. Note that this spirit can leave the body (especially during the sleep or a meditative state) and return. The need to check if your friend has a spirit within him is not necessary, as we all have a spirit within us, in the same way that we all have a heart that beats.
I have deliberately not answered your question by assuming that you are referring to negative entities, that can attach or follow persons. Should this be the specific nature of the question then please restate the question making it clearer.