After slaying Laban Nephi dons Laban's clothing (even every whit) and Laban's armor. Note that he specifically says that he does this after severing Laban's head. Clearly there was a significant amount of blood. Wasn't Nephi worried about wearing obviously bloodstained clothes?
"Laban was wearing armor, so that the only chance of dispatching him quickly, painlessly, and safely was to cut off his head - the conventional treatment of even petty criminals in the East, where beheading has always been by the sword, and where an executioner would be fined for failing to decapitate his victim at one clean stroke.... [Nephi] was an expert hunter, a skilled swordsman and a powerful man: with due care such a one could do a quick and efficient job and avoid getting much blood on himself. But why should he worry about that? There was not one chance in a thousand of meeting any honest citizen, and in the dark no one would notice the blood anyway. What they would notice would be the armor that Nephi put on, and which, like the sword, could easily be wiped clean. The donning of the armor was the natural and the shrewd thing for Nephi to do. A number of instances from the last war could be cited to show that a spy in the enemy camp is never so safe as when he is wearing the insignia of a high military official - providing he does not hang around too long, and Nephi had no intention of doing that. No one dares challenge "big brass" too closely (least of all a grim and hot-tempered Laban): their business is at all times "top secret", and their uniform gives them complete freedom to come and to go unquestioned." (Hugh Nibley An Approach to the Book of Mormon Deseret Book 1957, p. 99-100).