How Can custodial father prove non-custodial mother drugging child on visit with melatonin?

To prove that the non-custodial mother is drugging the child with melatonin during visits, the custodial father can gather evidence such as sleep patterns, behavioral changes in the child after visits, and any physical evidence of melatonin use, like leftover supplements or packaging. He might also consider documenting incidents with dates and times, and possibly obtaining testimonies from medical professionals if the child exhibits concerning symptoms. Additionally, he could request a drug test for the child if there is a strong suspicion of misuse. Consulting with a family law attorney can help navigate the legal implications and determine the best course of action.