Section 7.02(b) states “If, in the attempt to carry out a conspiracy to commit one felony, another felony is committed by one of the conspirators, all conspirators are guilty of the felony actually committed, though having no intent to commit it, if the offense was committed in furtherance of the unlawful purpose and was one that should have been anticipated as a result of the carrying out of the conspiracy.”
The law of party theory most commonly presented at trial is 7.02(a)(2), i.e. that a person intended to promote or assist in the crime being carried out, and solicits (seeks out a person to commit the crime), encourages (does acts to encourage the crime to be committed, including paying money for the crime), directs (orders the crime), aids, or attempts to aid in the crime. The typical case we think of is “murder for hire” in which someone pays another to kill their spouse, or the driver in the “getaway car” from a robbery, but the language is broad and attempts to bring in anyone who intends the crime to be committed and helps or encourages in any way. The jury will be instructed that “mere presence at the scene of an offense is no offense,” but anything more and things could start to get sticky.
The conspiracy statute, 7.02(b), is interesting and has been used in capital murder cases, and in a high profile gang rape recently in local courts. Basically, if two people conspire and agree to commit a felony (such a burglary/robbery/kidnapping/rape, and while trying to carry out that crime, another felony is committed by a member of the conspiracy/agreement, even if the person not intend that crime (carried out by a conspirator in furtherance of the offense) to be committed, if it should have been anticipated, other conspirators are liable under this theory. I.e. if you are committing armed robbery and kidnapping and murder is committed, which could reasonably be foreseeable, a conspirator who only intended to commit robbery could be guilty of the capital murder.