Being a lawyer is terrible. Having said that, if you want to be come a lawyer and in particular a criminal lawyer, I will give you some food for thought. To become a lawyer, in general, you need to graduate from an undergraduate school(Any major but most are poly-sci), take the LSAT, go to law school, take the MPRE and then the Bar exam. The whole process from beginning to end takes roughly 7 1/2 years but it could take longer.
The legal field is producing about twice as many graduates as are needed for the amount of law jobs available. Every year the glut gets bigger. Tuition is high, it is not uncommon for someone to graduate law school with 100K, 200K, 300K or more in debt and have no job. You hear and read about the stories of attorneys working as waiters, baristas, and retail clerks. I recommend that most people NOT go to law school. Currently 15 law schools are being sued for fraud by former law school graduates because they could not find jobs.
The medical field is the only profession where I routinely see people getting rewarded for going to school. However, many people still want to go to law school. Another sad aspect is that law school and the Bar exam teach you very little about how to practice law. If you want to practice law, law school is just a big waste of time, to get to the other side of actually being an attorney. You come out knowing very little, just enough to commit malpractice.
If you do decide to go to law school, go to the cheapest school you can, unless you get into Harvard, Yale, or Stanford. Don't pay big bucks to go some law school out of the top ten, it ain't worth it, even if the law school is ranked #20. Law schools and the legal profession are obssessed with law schools rankings. Lastly, try to work at a law firm part-time, even for free, in undergrad, to get a feel for the job and also have something to put on your resume.
If you decide to pursue law, good luck, you will need it. I wish I had a time machine where I could stop my undergrad self from going into law.
Should take you about 7 years after high school.
4 years for your bachelor's degree. Then take the LSAT and do well.
3 years for law school.
Then you need to pass the state bar exam in the state(s) you wish to practice law. You are then good to go be a criminal defense lawyer. Just starting out you might want to look into working for a public defenders office.