My son is 19 and had protected sex on August 30th just that time. She has a positive pregnancy test hcg levels 47730. She also said she had a abdominal ultra sound and saw heart beating. Is he a candidate?

Did the doctor say what she saw was a "heart beating" she may have seen what appeared to be.

First of course no form of protection is 100 percent, if his protection was just a condom they have a failure rate of 3 to 10 percent by some experts, and up to 20 percent failure quoted by other experts.

So if there is doubt, he will need to wait till the baby is born and require a DNA test.

All it takes is one time. Protected only makes it less likely, not impossible. A DNA test after its birth will prove he is or if its someone else's. I suggest getting it as soon as its possible. There have been many cases of the wrong guy being fingered as the father. You can't argue with DNA results. Not much anyway.

Assuming you mean 30 August 2011 and she's seen a heart beat then NO way is your son the father.
After all if he was the "baby" would not even be a month old and you cannot detect a heart beat at that stage.

Typically this cannot be heard with even a Doppler until the 9-10th week of pregnancy at the earliest, sometimes not until the 12-14th weeks of pregnancy.
Source: Fetal Heart Beat (http://pregnancy.about.com/cs/pregnancyphotos/l/blheartbeat.htm)

So all told the father is some one else.

Yes, the doctor said and showed the heart beating. In the last little few minutes she told him her primary doctor said the end of may 2012. I have checked on dna info and blood work can be done at 11 weeks. But its not adding up in my mind. She is 20 so also an adult. All I know is aug 30th 2011 was the date he was with her.

Sounds to me like someone isn't telling the entire truth here.
At a little over THREE weeks you wouldn't really even be classed as pregnant and certainly wouldn't see/hear the heart beat.
Ultrasound tests are not normally effective until after 12 weeks ( 3 months)!
So the due date is a fantasy as well, more likely March 2012 rather than May assuming is is indeed pregnant..

i have checked on dna info and blood work can be done at 11 weeks.

While it may be possible to determine paternity at that point it ain't going to happen. No doctor will do that just to determine paternity. No court will force it.

So your son waits until the child is born to have a test done.

Agree with Scott, no DNA test will be done till the child is born, there is too much danger in doing the early tests before births.

So it is really a wait and see till child is born

First of all the fetus has an heart beat within the first week of conseption... I have three children. How do you know he had protected sex, was you there for the whole sexual act monitoring? I have a 20 year old son myself, and they do lie.

How about this, wait for the child to be born and get a paternity test. Don't waste your time taking sides and possible find out that it is your grandchild. If it comes out not to be your grandchild, then give your son a good scare and a lecture on how you don't want to be involved in this kind of mess again or he will be on his own. If if comes out to be your grandchild, hopfully you have made yourselfe looks so bad that you can be involved in your grandchild's life and make your son know that he has to be a responsible man.