Towards the end of the Republic Roman masters gained the ability to free slaves inter amicos, or among friends. The disadvantage of this practice compared to manumissio vindicta is that while the friends may testify to the manumission, because there was no governmental official present, there was no legal record. As a result, manumissio vindicta was frequently even though the slave didn’t have to pretend to have originally been a Roman citizen. Manumissio vindicta was also popular with the government, because by requiring a governmental official be present at this ceremony the Romans could persuade themselves that they had some control over what kind of slaves became citizens. Indeed, the Romans passed a law called the lex Aelia Sentia that among other things tried to prohibit slaves who had ever been tortured or punished to work as gladiators from becoming Roman citizens. The Aelia Sentia also prohibited slaves who were younger than 30 from being manumitted, except in special circumstances.
However, the testimony of the jurist Gaius suggests that Roman officials had little interest in interrogating slaves whom their masters had manumitted. Gaius has the following to say about how manumissio vindicta is practiced in his day:
Maiores vero triginta annorum servi semper manumitti solent, adeo ut vel in transitu manumittantur, veluti cum praetor aut pro consule in balneum vel in theatrum eat.
The practice is that slaves over thirty are readily manumitted; it is such an everyday matter that manumissions are performed even en route from one place to another, for instance, when the praetor or proconsul is on the way to the baths or the theatre. (Trans. Gordon and Robinson, Institutes 1.20).