of a large work on Fidei commissa (Testamentary Trusts). As a hallmark of the increased connection between jurists and the imperial government, Antoninus' reign also saw the appearance of the Institutes of Gaius, an elementary legal textbook for beginners. Antoninus passed measures to facilitate the enfranchisement of slaves. Mostly, he favoured the principle of favor libertatis, giving the putative freedman the benefit of the doubt when the claim to freedom was not clearcut. Also, he punished the killing of a slave by his/her master without previous trial and determined that slaves could be forcibly sold to another master by a proconsul in cases of consistent mistreatment. Antoninus upheld the enforcement of contracts for selling of female slaves forbidding their further employment in prostitution. In criminal law, Antoninus introduced the important principle that accused persons are not to be treated as guilty before trial, as in the case of the irenarchs (see above). It was to Antoninus that the Christian apologist Justin Martyr addressed his defense of the Christian faith, reminding him of his father's (Emperor Hadrian's) rule that accusations against Christians required proof. Antoninus also asserted the principle that the trial was to be held, and the punishment inflicted, in the place where the crime had been committed. He mitigated the use of torture in examining slaves by certain limitations. Thus he prohibited the application of torture to children under fourteen years, though this rule had exceptions. However, it must be stressed that Antoninus extended, by means of a rescript, the use of torture as a means of obtaining evidence to pecuniary cases, when it had been applied up until then only in criminal cases. Also, already at the time torture of free men of low status (humiliores) had become legal, as proved by the fact that Antoninus exempted town councillors expressly from it, and also free men of high rank (honestiores) in general. One highlight during his reign occurred in 148, with the nine-hundredth anniversary of the foundation of Rome being celebrated by the hosting of magnificent games in Rome. It lasted a number of days, and a host of exotic animals were killed, including elephants, giraffes, tigers, rhinoceroses, crocodiles and hippopotamuses. While this increased Antoninus's popularity, the frugal emperor had to debase the Roman currency. He decreased the silver purity of the denarius from 89% to 83.5, the actual silver weight dropping from 2.88 grams to 2.68 grams.