Bite marks and their interpretations

 

Bite Marks

Interpretation of bite marks:

Police may sometimes bring objects for exami­nation like apple or piece of cheese. The unusual bite mark on the objects may be due to some dental abnormality. ‘Plastic’ marks on objects such as butter, cheese, lard, wax, or chocolates should be interpreted and for this they are to be stored in refrige­rator to prevent them from melting or flowing; they are not deep frozen as they may brittle and crack.

Figure: Human bite marks 

Nature of bite marks

Bite mark comprise of a crop of punctate haemorrhages varying from small petechial to large ecchymosis merging into a confluent central bruise.
Front teeth because bite marks from canine to canine with an invariable gap at either side representing the separation of upper and lower jaw.
A circular or shallow oval is human bite and deep parabolic arch or U shaped is characteristic of an animal bite. Teeth may cause clear separate marks that run in to each other as continuous, inter­mittently broken lines.
There may be abra­sions, bruises and lacerations or a combi­nation of all these. Suction petechial without teeth marks in sexual assault are caused by human bites, has a sucking effect and due to the rupture of small venules petechial haemorrhages result. Identification from bite marks is possible if inci­sors and canines have some char­acteristic features.

Bite mark investigation

Photographing bite mark, swabbing of saliva, Impression of bite mark, Skin carrying the bite is removed and preserved in formalin for future exami­na­tion.

Matching the bite mark with the suspect’s dentition: 

(1) Full informed consent before exami­nation of the suspect in writing to be taken 

(2) Oral consent with at least one witness, if not writ­ten to be taken 

(3) Dentition examined and points determined and recorded by diagram and writing 

(4) Photographs can be taken.

    The points to be noted in bite marks are: 

(i) Pre­sence of full or partial denture and were they worn at the time of incidence 

(ii) Number of teeth in the upper and lower jaw 

(iii) Charting of missing teeth 

(iv) Estimate of bite overhang; whether there is an edge-to-edge occlusion or an under­shoot projec­­tion of lower teeth 

(v) Recording of any broken teeth or teeth with significant individual abnor­ma­li­ties are charted and described 

(vi) Any irregu­larity or marked variation in cutting edge profile of any front teeth 

(vii) evaluation of size and promi­nence of any teeth especially canines and incisors 

(viii) Any developmental abnormalities are to be noted 

(ix) Recording of any abnormality in orienta­tion of any tooth such as twisting (rotation), antero­posterior tilting, double row of teeth or any gap or irregular spacing. 

For this: 

(a) six upper and six lower front teeth give the most information. 

(b) Canines may provide help 

(c) premolars and molars are rarely useful due to being poste­riorly positioned in the jaw.

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