For the bard interested in metamagic, metamagic song (races of stone) allows bardic music uses in lieu of higher spell levels. Also significant melodic casting, which allows casting while singing.
Looking at the bard's handbook, extend spell and captivating melody are good bets, as buffs and illusions are part of your stock in trade.
Unfortunately, that's about the extent of the things, and captivating melody is an even bet for someone going into sublime chord.
If you hadn't already started, I would have recommended bardic knack and jack of all trades into knowledge devotion, but that's a bit much to swallow mid-game.
Resurrection doesn't absolve anyone of a murder already committed
I may be getting a little close to real world religion here, but absolution comes from without, from the agency of another, not from one's self.
noun: formal release from guilt, obligation, or punishment.
While the spell undoes the effects of the crime, the act of harming was not undone. The situation you describe could be handled similarly to 'tort' law (in the Enlightenment / Western sense) rather than criminal law: one goes to court with the objective being that the crime victim be "made whole."
Beyond that, there are the issues of things like triple damages, right? evil grin
As you point out, the trauma of having been killed, even if the victim is subsequently resurrected, is not undone. Putting on our Feudal / Medieval / Renaissance era hat1, since that is what a lot of games like this try to assume as a setting, you still have the problem of "you did me wrong, I want to be made whole." You could apply something like a 'weregild' or even have the killer be declared 'outlaw' by the government as a consequence of the murder.
(Old English: “man payment”): in ancient Germanic law,
the amount of compensation paid by a person committing an offense to
the injured party or, in case of death, to his family.
To be declared outlaw ...
... was to suffer a form of civil or social death. The outlaw was debarred
from all civilized society. No one was allowed to give him food,
shelter, or any other sort of support—to do so was to commit the crime
of aiding and abetting, and to be in danger of the ban oneself.
Consequences: as Grandma said, you shouldn't have done that in the first place!
'Tis well that the court should acquit thee
'Twere best hadst thou never been tried
(From an old poem called "The Laws of the Navy")
Short answer? Treat it as a civil case, not a criminal case.
Cleric and wizard at level 13. They have access to 7th level regenerate. The cleric chose the noble backstory, and has a good bit of gold to burn.
Well, if he has money to burn, hit 'em with triple damages. The cost of the spell, times three, as a fine. Or, think through this like a "wrongful death" case and levy a huge judgment / fine that hits the cleric for about how much gold they have ... OK, they have to go and adventure some more, as they are now broke.
Money can't buy back a soiled reputation, nor buy absolution
Consequences? This (cleric) noble's reputation is tarnished. The party associating with that cleric is also held in a dim view per the old "you hang around with that crook?" vein of public shaming or rep harming. I suggest that you take a look in the DMG on the "Honor" optional ability score for ideas on how applying reputation or honor in game might be useful here.
You'll never work in this town again! (Exile)
They can still be exiled for having committed the murder, unless the weregild, or other suitable damages, are paid and they do a whole big public atonement deal. There is a nice Game of Thrones example: Cersei Lannister's walk of shame was such a public atonement, but did that really restore her rep? Maybe in the eyes of some.
An old school example
While not a 5e example, we had a party of 7-9th level characters who got into massive trouble with The King (AD&D 1e). Why? We killed the heir (we didn't know he was the heir; he was running a side scam with a Thieves Guild). We were able to afford a raise dead spell, and we paid for it, but the King was not amused with our assault on his bloodline.
We were declared outlaws. As a result, we fled the kingdom and undertook adventures elsewhere. And, we did have to contend with bounty hunters for the rest of that campaign.
1 @pboss3010 raises the valid point that there's no reason to apply "modern" legal thinking. Your typical medieval fantasy has no reason to have a Bill of Rights. Double jeopardy, cruel and unusual punishment, no speedy trial, all of these are in play
A "school" of magic is just a category of magic; an academy which teaches multiple schools of magic is valid and appears in D&D canon.
A "school" of magic is not an actual institute of education, but rather the term refers to a type of magic. A place of magical learning is typically called a magical university, college of wizardry, or some other name.
This is best described in the AD&D 2nd edition Player's Handbook (revised, p.44):
Colleges or guilds may specialize in one school of magic, although a Hogwarts-style academy which teaches all schools of magic in separate classes is also valid. Colleges of both types appear in D&D lore.
For example, the Bleak Academy (Tome and Blood p.25) specifically teaches necromancy, while the Arcane Order (Tome and Blood p.23; and detailed at length in the AD&D 2nd edition book College of Wizardry) teaches all schools of magic. This is specifically stated in College of Wizardry, p. 25-26:
For completeness, other editions of D&D largely concur with AD&D's definition of a spell school. D&D 3.5 Player's Handbook, p. 172:
D&D 5th edition describes each school of magic as a separate ancient arcane tradition (Player's Handbook, p.115):
D&D 4th edition uniquely broke from this tradition, and its Player's Handbook only uses "school" to refer to an arcane academy:
AD&D 1st edition's Players Handbook didn't yet use the term "school", instead referring to it as "type" of magic. In the earlier question What is the origin and meaning of D&D Beyond's spell school symbols?, we see that AD&D 2nd edition introduced both the term "schools" and the symbols for those schools. This may be because 1st edition only include one specialist wizard, the Illusionist, while 2nd edition had the possibility of a specialist in any type of magic, and thus there needed to be a better name for types of magic, and the concept of opposed schools represented in the diagram.