What constitutes a breach of a bail bond contract by the defendant?

Failing to appear in court is considered a breach of a bail bond contract because it directly violates the fundamental condition upon which bail is granted. When a defendant is released on bail, it is typically under the agreement that they will return to court for their scheduled appearances. The purpose of the bail is to ensure the defendant's presence in court; therefore, a failure to appear signifies a serious breach of the contract between the defendant and the court, as well as between the defendant and the bail bond company.

In this context, all other options involve aspects that may not directly contravene the basic terms of the bail bond. For instance, paying the bond late might lead to financial implications or penalties but does not inherently prevent the defendant's presence in court. Changing address without notice could lead to communication issues but does not itself constitute a breach unless it results in missed court appearances. Requesting a bond transfer may be part of managing the bond arrangement but doesn’t violate the terms of the bond agreement unless it's not done correctly. Thus, the most clear and unequivocal breach of the bail bond contract is failing to appear in court.