>検察側の証人 = A witness for the prosecution >Isn't the same to say 検察の証人 ? Yes, it is same. You use "側(side)", when there are two sides and you want to emphasize which side you(or someone) are on. 検察側の証人 vs　弁護側の証人 経営側の人間 ｖｓ　雇用側の人間 ※ 検察の証人 is sytacatically right. But I personally never have heard/read this word. That's probably because there are always two sides in the court, offeder and deffender. In this usage , the pronounciation is always "gawa", never "soba".

Hi! 側 is read がわ in this context, and it means "standpoint", "side", "party", etc., all of which amounts to "person(s) involved" in the action described just before the 側. 検察側の証人 can be translated as (witnesses concerned with the prosecution). 検察の証人 is translated to (prosecution witnesses). As for being pronounced (そば), it's when you refer to a position of a place. Example: 喫茶店のそばに本屋がある。--> There is a bookstore near the coffee shop. For (がわ), you mainly use it as stated previously or with directions like: 右側 "right side"　左側 "left side" Hope this helps.