Ans; B (Locard Exchange Principle) Locard's Exchange PrincipleQWhen any two objects come into contact, there is always a transfer of material from each object to the other. Traces from the scene may be carried away on the person or tools of crim in a l & at the same time, traces from all or any of these may be left at the scene.Whenever a criminal goes, whatever he touches, & whatever he leaves will serve as silent evidence against him. e.g. fingerprints, footprints, hair, fibres from clothes, broken glass, too! marks, paints, scratches, blood or seminal stains etc.It is actual evidence1' & its presence is absolute proof of the crime.Locards MethodQ# The ridges of the fingers & hands are studded with minute pores which are the mouth of ducts of sweat glands situated below the epidermis. These pores are permanent & differ in no., size, shape & arrangement for a given area in each individual.# This method of identification by examining the pores is known as poroscopy1 or Locard s method# This is very useful when only a part of the fingerprint or a fragmentary print is available for examination & identification.Mc Naughten RuleQ (the right or wrong test: The legal testQ)# "Nothing is an offence which is done by a person, who at the time of doing it, by reason of unsoundness of mind, is incapable of knowing the nature of the act, or that he is doing what is either wrong or contrary to law"# This law is included in sec. 84 I.P.CdRule of HaaseQ# This is a rough method of calculating the age of foetus . The lenght of the foetus is measured from the crown to the heel in cm..During the first five months of pregnancy the square root of the length gives the approximate age of the foetus in months.During the last five months, the length in cm. divided by five gives the age in months.