Yes you can get child support from the date your son was born, if the alleged father is determined to be the legal father. Yes you can garnish his wages for that support. Generally the DNA testing is done through Child Support Enforcement which is different than DFS, which is now called Children's Division. If you are talking about the DNA testing timeframe, it depends on how soon they can get all of the parties in to be tested. Once all parties have submitted DNA samples, it generally only takes a week or two to get the results.
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Yes and yes although it's usually retroactive to the date the case was filed. The process is usually a few months although there's no set amount of time. I'm licensed in California and it's always best to confirm with a lawyer licensed in your state.