No Deacon can, save under very exceptional circumstances, be ordained Priest before he is 24, and has served at least a year in the Diaconate.
Fitness.
This fitness, as in Confirmation, will be intellectual and moral. His intellectual fitness is tested by the Bishop's Examining Chaplain some time before the Ordination to the Priesthood, and, in doubtful cases, by the Bishop himself.
His moral fitness is tested by the Publication during Service, in the Church where he is Deacon, of his intention to offer himself as a Candidate for the Priesthood. To certify that this has been done, this Publication must be signed by the Churchwarden, representing the laity, and by the Incumbent, representing the Clergy and responsible to the Bishop.
Further safeguard is secured by letters of Testimony from three Beneficed Clergy, who have known the Candidate well either for the past three years, or during the term of his Diaconate.
Finally, at the very last moment, in the Ordination Service itself, the Bishop invites the laity, if they know "any impediment or notable crime" disqualifying the Candidate from being ordained Priest, to "come forth in the Name of God, and show what the crime or impediment is".
Why all these safeguards? For many obvious reasons, but specially for one. Priest's Orders are indelible.
The Indelibility of Orders.
Once a Priest, always a Priest. When once the Bishop has ordained a Deacon to the Priesthood, there is no going back. The law, ecclesiastical or civil, may deprive him of the right to exercise his Office, but no power can deprive him of the Office itself.
For instance, to safeguard the Church, and for the sake of the laity, a Priest may, for various offences, be what is commonly called "unfrocked". He may be degraded, temporarily suspended, or permanently forbidden to officiate in any part of the Church; but he does not cease to be a Priest. Any Priestly act, rightly and duly performed, would be valid, though irregular. It would be for the people's good, though it would be to his own hurt.