Depends on the reason for which it is used. Just because he posts it on FB does not make it true, especially if he is only 19. People post stupid things on FB that are not always true just to impress others. It is your burden of proof to show that his is taking drugs and it is effecting his ability to parent.
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If the court believes there are drugs or alcohol involved, the court likely will order drug testing. If you present printouts of the father's postings, the court likely will order drug test, probably hair follicle testing.
If the father has been taking drugs in the last 2-3 months, the results of the drug testing likely will show the usage.
You should review the specific facts with your attorney to find out your legal options.
This is an interesting question because, if he says it is not true, then he was lying on Facebook, and the court will wonder why? If it is true, then the court will want to do at least an immediate UA and if he is drinking a lot, an ETG. At the very least, it will demonstrate that he is fixated on drinking and drugs.
What I do not know is the status of your case. Is there a parenting plan already in place? Is paternity established? Is he ordered to pay support under an administrative order? It may be best just to leave things well enough alone. Good Luck.
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