Inside of dock, defendant’s first caught by forensic traces and shuts off (8)

'shuts off' is the definition.
The answer and definition can be both to do with contact as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?

'inside of dock defendant's first caught by forensic traces' is the wordplay.
'inside of' says to take the centre.
'defendant's first' becomes 'd' (cst letter of 'defendant').
'caught by' indicates putting letters inside.
'forensic traces' becomes 'clues' (I can't justify this - if you can you should believe this answer much more).
The centre of 'dock' is 'oc'.
'd' going inside 'clues' is 'cludes'.
'oc'+'cludes'='OCCLUDES'

'and' is the link.

Can you help me to learn more?