if one was arrested on aggravated assault with deadly weapon charges but no weapon was found and the victim says that the defendent did not have a weapon but and eyewitness says the defendent did can the case be beaten
Not necessarily. The prosecutor and police will interview all witneeses. Additionally, they know that victims chnge their testimony if they have a relationship with the victim, such as husband and wife or boyfriend and girlfriend. This a question that needs to be discussed thoroughly with a good criminal defense attorney.
The complainant is a witness just as the eye witnesses are witnesses. The State can proceed on an aggravated charge with the testimony / evidence given by the non-complainant witnesses, even if there are not injuries.
That said, your lawyer may be able to fight the case on the basis of the complainant's view - depending on the circumstances. (If it is family violence, then the State tends to give much less weight to any claims made by the complainant.)
You present an interesting question.
There are several ways the prosecution may prove its case, one is called by direct evidence (the actual weapon present and entered into evidence) and corroborating evidence (the actual weapon not recovered yet the case witnesses testify to one being used in a commission of the alleged offense). You case seems to fall into the latter category.
In my practice, I have seen seemingly simple cases get complicated and, conversely, complex issues that were won on a technicality.
The only way to address the given case is to retain a capable and determined criminal defense attorney in San Antonio, TX who will defend the case by selecting the best strategy that will use all the case facts.