Assault and battery are not the same criminal offense, they are two separate crimes. Battery requires some sort of physical contact. Assault does not require actual physical contact. As such, an assault can take place even when no battery (offensive touching) occurs. You will often here assault referred to as an attempted battery.
Even the slightest unwanted touching can result in a criminal charge for battery under California Penal Code 242. The prosecutor will be looking for facts in the police report which demonstrate that the touching was (1) willful; (2) unwanted, and (3) harmful/offensive. A battery charge is still possible even if the suspect caused no injury to the alleged victim. Depending on the type or degree of injury to the victim, the prosecutor has discretion to file several different criminal offenses.
If there was no injury, it is common for the prosecutor's office to file misdemeanor charges. If the injury caused serious bodily injury, the offense may be charged under Penal Code 243(d) - a battery causing serious bodily injury. If the victim is a police officer, the charge may be under Penal Code 243 - battery on a peace officer.
Matthew B. Wallin