Iudex dicit nefas esse innocentem damnare, fas autem esse etiam impio veniam dare, si veritatem tandem dicat.

Because Latin very often reports statements with an indirect statement construction: a verb of saying, thinking, knowing, etc. + an infinitive.

So instead of something like The judge says that it is wrong..., Latin says literally:

• Iudex dicit nefas esse... = The judge says it to be wrong...

And then:

• fas autem esse... = but to be right...

This is a standard Latin pattern after verbs like dico.

In many indirect statements, Latin has an accusative subject + infinitive, for example:

• dicit eum venire = he says that he is coming

But here the core expressions are fas est and nefas est, which are impersonal. They do not normally take a personal subject like he or they.

Instead, the infinitive phrase itself functions as the thing being judged:

• nefas esse innocentem damnare = that condemning an innocent person is wrong
• fas esse etiam impio veniam dare = that giving pardon even to a wicked man is right

So there is no separate accusative subject because the statement is built around an impersonal expression.

Fas and nefas are important Latin words meaning something like:

• fas = what is permitted by divine or moral law; what is right
• nefas = what is forbidden by divine or moral law; what is wrong, impious, outrageous

They are not just ordinary adjectives like good and bad. They carry a stronger sense of right vs. taboo / morally forbidden, often with a religious or sacred flavor.

In this sentence:

• nefas esse innocentem damnare = to condemn an innocent person is wrong
• fas esse... veniam dare = to grant pardon... is right

Because innocentem is the direct object of damnare.

• damnare = to condemn
• innocentem damnare = to condemn an innocent person

So:

• innocentem is accusative singular
• it means an innocent person or the innocent person

Latin often uses an adjective by itself as a noun when the noun is understood. So innocentem here means something like innocentem hominem.

Because impio depends on veniam dare.

• veniam dare alicui = to give pardon to someone
• veniam is the thing given, so it is accusative
• impio is the recipient, so it is dative

So:

• veniam dare = to grant pardon
• impio veniam dare = to grant pardon to a wicked man

This is like the normal pattern of giving in Latin:

• librum puero do = I give a book to the boy

Here:

• veniam = the thing given
• impio = the person receiving it

Yes, it is a very common Latin expression.

• venia = favor, indulgence, pardon, forgiveness
• veniam dare = to grant pardon / to forgive / to show mercy

So although it literally means to give pardon, in smoother English it often becomes:

• to pardon
• to forgive
• to grant mercy

Because autem is a postpositive word in Latin. That means it usually comes second, not first.

So Latin says:

• fas autem esse...

not usually:

• autem fas esse...

A natural way to understand it is:

• but, on the other hand, it is right...

Other common postpositive words behave similarly, such as enim and igitur.

Etiam means also, even, or still, depending on context.

Here it most naturally means even:

• etiam impio veniam dare = to grant pardon even to a wicked man

It emphasizes that mercy is being extended to someone you might not expect to receive it.

The main reason is that this si clause is inside indirect speech.

The whole idea being reported after dicit is:

• it is wrong to condemn an innocent person,
• but right to pardon even a wicked man,
• if he finally tells the truth

In Latin, subordinate clauses inside reported speech are very often put into the subjunctive. So dicat is not there because si always takes the subjunctive—normally it does not. It is subjunctive because the condition is part of what the judge is saying.

So the sense is:

• The judge says that ... it is right ... if he should / if he does finally tell the truth

It can sound somewhat more general or less bluntly factual than a plain indicative would.

Very roughly:

• si ... dicit would feel more straightforwardly factual in direct speech
• si ... dicat here, inside indirect speech, presents the condition as part of the reported idea

In context, it means something like:

• if he does finally tell the truth
• provided that he finally tells the truth

So the sentence is not saying pardon should be given unconditionally; it is tied to that condition.

It is an implied he.

Latin often leaves subject pronouns unstated when the verb ending already shows the person and number.

• dicat = he/she/it may say or, here in context, he says / should say within reported speech

Because of the nearby impio, the understood subject is naturally the same person:

• even to a wicked man ... if he finally tells the truth

So the meaning is:

• pardon should be given even to a wicked man, if that man finally tells the truth

Veritatem is accusative singular because it is the direct object of dicat.

• veritas = truth
• veritatem dicere = to speak the truth / tell the truth

So:

• si veritatem tandem dicat = if he finally tells the truth

This is a very common Latin expression.

Tandem means at last, finally, or sometimes after all.

Here it means:

• if he finally tells the truth

It suggests delay, reluctance, or frustration: the person has not been truthful before, but eventually may speak honestly.

Because those infinitives are the actions being judged as right or wrong.

• innocentem damnare = to condemn an innocent person
• impio veniam dare = to grant pardon to a wicked man

With fas est and nefas est, Latin commonly uses an infinitive to express the action under discussion:

• fas est hoc facere = it is right to do this
• nefas est mentiri = it is wrong to lie

So in your sentence, the infinitives are not unusual at all; they are exactly what Latin normally uses with these impersonal expressions.

Not necessarily. Latin singular can be used in a general sense.

So innocentem damnare can mean:

• to condemn an innocent person
• to condemn the innocent

Likewise impio can mean:

• to a wicked man
• to a wicked person

The singular does not have to refer to one specific individual; it can express a general principle.

Yes. Latin often uses adjectives substantively, meaning the adjective itself functions like a noun.

So:

• innocentem = an innocent person
• impio = to a wicked person

An underlying noun like hominem or viro is simply omitted because it is easy to understand.

This is extremely common in Latin and something English speakers need to get used to.