from an online forensic science site article..
4. fingertip/pad bruises
Where an assailant has forcefully gripped a person, for example around the neck (e.g. during attempted manual strangulation) or arms etc, one may see small discoid or ovoid bruises in a cluster. These may be discrete, but are often blurred or may 'merge' with one another, due to the dynamic nature of assaults and struggles with an assailant. Sites to look for these bruises include,
The neck
The arms
The face and trunk in children
The inner thighs in suspected sexual assault