Part1

Is there any US law covering the area/subject of a defence lawyer colluding with his client to pervert the course of justice. For example, if the lawyer knows of damning facts that clearly incriminate his client or if he believes in some other evidentiary way that his client is guilty?
What would happen to a lawyer who did this (if it is in fact a crime in the US)?

Part 2

Is it also possible for someone to be tried in their absence? For example, the person is extremely ill, but he has a lawyer who acts on his behalf in court.

The number of lawyers who have colluded with clients in order to pervert the law is that many. For example, take the matter of the client's guilt or innocence. If the client is guilty and lets his lawyer know, he will immediately be advised to plead if that lawyer is honest. A case of say, perjuring yourself would certainly be cause for complaint to the ABA.

Trials of defendents are held in absentia all the time. They require certain circumstances, which I'm not sure enough of to state here.

Catty

This is how we proceed in the UK. I do not doubt that the Bar in the USA follows the same basic principles, however. Every counsel is asked 'How can you defend a man whom you know to be guilty?' It is not our concern. It is the jury's. He or she would fail the clients, justice and all fellow citizens if we made it so . It applies however strong the evidence may be against him may seem and however vile he may appear to the world. The accused is presumed to be innocent. It is difficult for a layman to understand how, for the trial at least, the question is not in our minds. What is is 'How are we doing?'! Now, what happens if the accused tells us he is guilty but wishes to contest the case? If he insists we tell him that we can only continue to act for him under certain conditions. First we cannot call him or any other witness to testify in his defence.Second we cannot put a false case to witnesses. Third we can only address the jury on one question which is,'Are you satisfied beyond reasonable doubt on the evidence that the prosecution have proved that the accused is guilty?' and we may point out any deficiencies that they might find in it, but no more . It is not unknown for such a client to be acquitted and his co-accused who had denied all and testified be convicted.This seems odd but highlights the burden and standard of proof that exists.An acquittal strictly speaking, it may be cynically said, is no more than a failure by the prosecution to prove guilt, not a proof of innocence! If counsel is told of supposed evidence against his client or encounters documents tending to incriminate his client in the crime before the court he has really no more duty to tell the police than his client has. He should however, ask his client about them and then proceed according to whatever his clients instructions about them are; he then proceeds as above. Of course, over all this is the principle that counsel must not knowingly allow himself to be an instrument in the actual commission of crime . ( This is why he can't call the client to commit what he knows, from his own lips, would be perjury )Finally there is 'professional embarrassment'which arises where counsel no longer feels that he can do justice to the client or the court . This may be because of a conflict between the client and counsel e.g. because the client claims to have no confidence in counsel or instructs counsel to proceed in some way which is illegal or contrary to the code of conduct of the Bar. In such cases counsel declares that he can no longer act and withdraws.