Obviously I don't know your sons tax situation or income but it's possible he may qualify for the earned income credit (EIC) that was introduced some time ago to help those with minimal income. It's a refundable credit so you can have a return greater than what you paid in taxes. The EIC was established to help those people who are trying to help themselves by working at a legitimate job even if they don't make a lot of money. Some people who have also been laid off in the calendar year qualify for EIC as their income level has dropped. If he needs assistance in filing his taxes and determining his legitimate deductions and credits he can go to an AARP Tax Site and have his taxes prepared for free. If he's already prepared his return he may ask at the AARP site if they would review his return. If he's made errors the return can be amended.
As far as the drug dealers, the only way they would receive a tax return of $5,000.00 plus is if they filed and were eligible for refundable credits. It's possible if they had a spouse working or they had a job for part of the year that would qualify them for EIC. Technically your're supposed to report all income, legal or otherwise, on your return including revenue from the sale of illegal drugs. Al Capone wasn't arrested for being a gangster - he was arrested for income tax evasion and not reporting income.
Here are refundable credits that can lead to a substantial return:
Earned income credit
Adoption credit
First time homebuyer credit (for past years)
Additional child tax credit
Health coverage tax credit
American opportunity credit
An earlier post referenced a woman with an $8,000.00 refund and it would be my guess that she qualified for EIC. Even if you file a correct W-4 you still have the potential to receive a tax return far in excess of what you've paid, if any, into the system.
The tax system is too complex and I agree that a flat tax is the way to go but I doubt we'll see it in our lifetime.