Medical Jurisprudence, Forensic medicine and Toxicology. Vol. 1

by R. A. Witthaus; Tracy C. Becker

Some cutting weapons, like an axe, act as much by means of their weight as by their cutting edges. Wounds caused by such weapons we can often distinguish by the following signs: The edges are not as smooth as is the case with a cutting instrument, and they may be more or less lacerated and show signs of contusion. The wound is often deep in comparison with its length, and the ends of the wound abrupt instead of slanting up from the bottom to the surface. The section of resisting organs and the impression of the edge of the weapon on the bone are further signs of the use of such a weapon.

The form and direction of a wound may possibly give some indication of the form of the instrument—for instance, whether it be straight or curved like a pruning-knife, as in the case cited by Vibert[636] of a wound of the neck which suddenly became deeper toward its extremity and changed its direction; the whole being explained on the supposition that it was made by a pruning-knife.

But it is in punctured wounds especially that we are enabled most often and most accurately to determine the kind of a weapon used. Here from the form of the wound we may judge of the form and size of the weapon. In speaking of punctured wounds in a former section we divided them into four groups, reference to which may here be made. In the first group, or those caused by cylindrical or conical weapons, when the weapon is very fine it may leave no track at all; if a little larger, we may infer from a linear bloody track that the weapon was needle-like in shape. The length of the instrument or the depth to which it penetrated may be found, as a rule, only by dissection. If the weapon were larger and conical, we have seen that the wounds would be linear with two angles, the length of the wound being parallel to the direction of the fibres in the skin.

Here we may judge of the form of the weapon from the following circumstances: From a comparison of the depth with the size of the opening, we know that it was a punctured wound. The edges and angles are not smooth and even enough for a stab-wound with a knife, for the edges are torn and not cut, and a stab-wound would be the only form of wound with which we would be likely to confuse it. Furthermore, the direction of the long axis of the wound parallel to that of the skin fibres in the region in which it occurs and the very slight retraction of the edges distinguish it from a stab-wound. By these signs we can almost always distinguish such wounds from stab-wounds, and thus tell the form of the weapon used. As to the size of weapon used, these wounds if of any size are generally smaller than the weapon, for the skin is put on the stretch by the weapon and yields to a certain extent. The actual wound, therefore, is smaller in circumference than the weapon. The size of the wound is smaller than that part of the weapon occupying the wound when the weapon was arrested; it may be very much smaller than the weapon at its largest point. Small wounds of this kind are generally larger than the instrument producing them.

The second group of punctured wounds, or stab-wounds, are by far the most common and, therefore, the most important variety of punctured wounds. If the stab-wound is perpendicular to the surface the form of the wound may represent pretty closely that of the weapon at the point where the latter was arrested, whether it has a single or double cutting edge. But even here there are exceptions. Frequently a weapon with a broad back and only one cutting edge may produce a wound resembling that of an instrument with two cutting edges, the second angle tearing as in the former class. Here on close examination we can sometimes distinguish the difference between the two angles, and judge correctly of the shape of the weapon. In fact, wounds made by common pocket-knives are regularly slit-like and not wedge-shaped, as the wound is caused only by the cutting edge of the knife. Again, if the single cutting edge is blunt, in rare cases the wound is produced in the same manner as those of the first group, or conical and cylindrical instruments. We would be led to suppose that the wound was produced by such an instrument, as both angles are torn, unless the direction of the wound might not follow that of the fibres of the skin, in which case we would be left in doubt. Stab-wounds are sometimes angular from the knife being withdrawn in a slightly different direction from that in which it was introduced or from an unequal retraction of the skin (see Fig. 9). If the stab-wound is obliquely directed, we can still judge of the general shape of the weapon, with exception of the cases above mentioned. The dimensions and size of the weapon are here much harder to determine. The dimensions of a stab-wound in the skin may be the same as those of the weapon, or of that part of the weapon which is arrested in the wound, but often they are not so. To measure the size of a wound exactly so as to get at the exact size of the instrument, we should place the region of the wound in the same position, etc., that it was when the wound was inflicted, and this we cannot often do. As the skin was tense or relaxed at the time the wound was inflicted, so the wound in the skin appears smaller or larger, just as with a sheet of rubber under similar conditions. If the instrument is very blunt, the wound in the skin may be smaller than the weapon whether the skin near the wound is tense or not. Thus Hofmann saw the wound from a blunt bayonet one centimetre shorter than the weapon.

The wound of the skin may be shorter and broader than the weapon used on account of retraction of the edges of the wound, and this is especially marked when the wound lies transversely to the direction of the skin fibres. On the other hand, the length of the external wound is more often greater than that of the weapon, because the wound is elongated by making pressure toward the cutting edge on withdrawal of the weapon, and an oblique wound measures longer than the weapon. If the blow is from above downward and the cutting edge of the weapon is uppermost, the length of the wound is not so likely to be increased much beyond the measurement of the weapon as when the cutting edge is directed downward. There is but one condition in which a stab-wound is at all likely to correspond in dimensions with that of the weapon, and that is when the wound is perpendicular to the surface. Even here the wound may be lengthened on withdrawal of the weapon, and we have to allow for retraction of the edges and try to put the parts in the same condition of tension or laxity as at the time of wounding. Even in the most favorable case, therefore, we cannot with certainty tell the exact size of the weapon. If a stab-wound be directed obliquely to the surface, then the length of the wound is greater than that of the weapon, unless this increase be exactly counterbalanced by the lateral retraction of the wound. The size of the weapon in such oblique wounds is further obscured by the changes of size due to withdrawal of the weapon, retraction of the edges, and the condition of the tension of the skin at the time the wound was inflicted.

Fig. 9.—Angular Stab-Wounds of the Anterior Chest Wall caused by a Strong Pocket-Knife.

Dupuytren remarks that stab-wounds are smaller than the weapon owing to the elasticity of the skin, but a lateral motion of the weapon may cause considerable enlargement of the wound. If a stab-wound has traversed a part of the body, the wound of exit is smaller than that of entrance.

The depth of a punctured wound may be any part of the length of the weapon, or it may even be deeper than the length of the weapon owing to a depression of the surface by the force of the blow, or the pressure of the handle of the weapon or the hand holding it. We have already seen that this may occur in a marked degree in penetrating wounds of the abdomen involving one of the movable viscera, also in wounds of the thorax, partly from depression of the surface and partly from an expansion of the thorax when opened at the autopsy, thus increasing the measured depth of the wound. Punctured wounds of the third class made by instruments with ridges or edges, like foils, files, etc., present more or less the shape of the weapon if the edges are cutting, but not always so if the direction of the wound be oblique or the parts unevenly stretched. If the edges are not cutting they cause wounds more or less like the first class of punctured wounds, but we can often distinguish them from the latter by little tears in the edges. The entrance and exit wounds may not be alike.