Child Abuse

[WayneAD]

I have a cousin who has full custody of her child. (texas). The child was phsically abuse by his step mom. CPS was notified and determine to an extent that the child was abuse, but after further investigation they determine that the child showed no visibile abuse. The child father and step mom told them that the child was lying and that the child real mother is making him say these thng. Would it be illegal for my cousin to hire a Private Investigtor to search out the truth and follow this step mom. Can you plant some type of device in her apartment to catch her abusing this child? My cousin is very afraid for her son. The child father is always working and never spends time with his son. The step mom who is around 19yrs old and is the one that takes her of the child. The father is 30yr old man. Any advice anyone?