Once they try to serve you on 3 different days, they can then leave the papers with someone over 18 at the residence, followed by 1st class mailing of the summons and complaint. Service is deemed complete 10 days after the mailing. you mthen have 30 days from completion of service to file an answer. I have never researched what happens if papers mailed first and then left with someone later at the residence. I wouldnt risk problems with having a default over a possible defect like that in service. If you have the papers, you should get legal advice now on the merits of the action.
Usually sub-service is supported by a declaration that the person made 3 attempts to serve you in person, and then left the summons with someone at your house and followed up by mail.
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The code calls for mailing AFTER the papers are dropped off. As Mr. Kopelson points out, if the papers were mailed first, it raises an interesting legal issue. I also agree with him that the best route (and cheapest/most efficient in the long run) is likely to face the merits of the lawsuit and have the allegations against you evaluated by an attorney.
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