I have not been able to get the decocking lever to work without first pulling the trigger to releas the hammer.  I don't think that is correct especially after reading the manual.  I have not loaded the gun so no ammo is involved.  Is there anything tht would prevent the decocking lever from functioning? Does the magazine have to be in the pistol for the decocking lever to work?

The decocker should work at all times, with or without mag inserted. Sounds to me like the decocker spring may be off track. Have you taken off the grips to take a closer look at the decocking mechanism? If the spring is in place, you have another problem altogether, and I'd advise a visit to a gunsmith, or a trip back to SIG. Out of curiousity, have any mods been done to your pistol?
B9

I would suspect either the spring, or more likely, the grips themselves. Try taking off the grips and VERY carefully observe the action. The decocker should work smoothly and gently lower the hammer.

Thanks for replying.  When I got home I tried the decocker again.  Apparently I was not pressing down far enough for it to engage.  I waws stopping when I felt resistance.  The only pistol with a decocker I have experience with is hte Beretta 92.  Yes the decocker works with or without the magazine and when cocked through cycling the slide or manually cocking by pulling back the hammer.

I purchased the pistol NIB yesterday, no modifications and I have resisted the urge to take off the grips to see the inner workings.  I appreciate the timely response and sound advice.