Dear Chas:

There are consequences that we must live with all our lives, even though the sin has been forgiven. For example, if I drink drunk and crash leaving myself and a bystander paraplegic, I can be forgiven for the sin, but both myself and the bystander must live with the consequences for the rest of our lives.

Sin and consequences are two separate things. Sin can always be forgiven, but we must still deal with consequences.

 As for the wrong this fella did in his past, the Church teaches that for a sin to be mortal three things must be true:

1) the sin must be grave (this is an objective reality)
2) the person must know that the sin is grave
3) there must be full and unimpaired consent to commit the sin

The third criteria is the operative one. If anything impairs one's ability to make a truly free choice, then they may be in what is called diminished responsibility. This means that their culpability "may" be reduced (CCC 1735, 1860). We see this in our court system where a person murders someone but is found innocent by reason of insanity. This concept came from the Catholic Church.

This, and the second criteria, may reduce the culpability even for an atheist. The Catechism mentions this (CCC 2125). Two other examples of possible diminished responsibility are found CCC 2355 concerning prostitution, and CCC 2352b concerning pornography and masturbation.

Diminished responsibility is a possibility, but in most cases only God knows where the lines are drawn, thus we cannot be arrogant to presume we do not need to confess any grave sin. All grave sins need to be confessed regardless.

You are in error in saying Baptism washes away all sin AND consequences. Baptism washes away all pre-baptismal sins only. If I drove drunk, as in my example above, before I was baptized, getting baptized does not heal me or the bystander from being paraplegic. 

Baptism does provide the person with a clean slate. They are in a state of grace the moment they are baptized and stay that way until they next sin gravely.

It is not proper, in my opinion, for you to advise this person to not confess pre-baptismal sins. To begin with, I believe that most of the time candidates for baptism receive Confession before the Easter vigil, I think, not sure. In any event, there is a kind of confession called a general confession. This is a life review and involves confessing all sins even those already absolved. The purpose of this is to review one's life, the ark and trends of one's life. This has great psychological value. It also helps people to know that their sins are truly forgiven.

In my opinion, those baptized, if they did not go through confession beforehand, will benefit from a general confession to help them understand the trends of sin in their lives, which helps to avoid those sins in the future, and to bring it home more acutely that their sins are truly forgiven.

As far as a criminal record, those consequences generally never go away completely. It depends on the situation and the jobs sought after. In any event, as it is with all of us, God will help us if we let him. Romans 8:28 says, "We know that in everything God works for good with those who love him, who are called according to his purpose."

That means that all things, good and bad, are made good by God. Or to put it another way, when we lay lemons in our lives, or life itself gives us lemons, God will make sweet lemonade if we let him.

You did okay for the most part, but you need to be more precise and careful with what you advise. 

God Bless,
Bro. Ignatius Mary