Question: Would having a tattoo and/or the previous breaking of God’s commandments prevent a gentile from converting to Judaism?
Answer: Like it or not, Jewish law has really different demands for Jews and non-Jews. The 613 commandments–which include everything from “be fruitful and multiply” to “no wearing clothes made of linen and wool together”–apply specifically to Jews. According to Jewish tradition, non-Jews are only responsible for seven commandments: the seven Noahide laws (no idolatry, murder, theft, incest, or blasphemy, no eating the flesh of an animal while it is still alive, and an obligation to set up a just legal system).
If a non-Jew wants to practice some of the mitzvot, such as keeping kosher, she is permitted to do so, but she should hold off on completely fulfilling the mitzvot that are meant as specific signs between God and the Jewish people, like wrapping tefillin, kissing the mezuzah, saying Shema, or full on keeping Shabbat.
A non-Jew who is interested in converting will probably be encouraged by her rabbi to begin taking on mitzvot, studying, and attending community functions. The rabbi she’s working with will likely discuss with her all kinds of issues relevant to her desire to become a Jew, and how she thinks it will change her life. Mainly, they will talk about the future, and future decisions. Things she did in the past–whether it’s getting a tattoo, eating a ham sandwich, or working on Shabbat–are not especially relevant, since she wasn’t Jewish, and thus wasn’t obligated to observe the tenets of the Torah.
If she says to the rabbi that she loves getting tattoos and/or eating ham sandwiches so much that she doesn’t think she’ll be able to stop, even after she has converted–well, that could be a problem. But if she did them at a different stage in her life, before Judaism came into play–that’s no problem at all.
Additionally, Jewish law forbids getting a tattoo, not having a tattoo. There is no prohibition against having a tattoo, regardless of whether it was inked while you were Jewish or not. And once you have a tattoo, getting it removed is optional. If you find it to be embarrassing, or in some way a reminder of a lifestyle or behavior you no longer like, halakha strongly prefers the laser surgery method of removal, as opposed to the alternative, plastic surgery, which could be considered voluntary bodily harm. And by the way, despite anything you may have heard, having a tattoo won’t prevent you from being buried in a Jewish cemetery.
The point is, if you’re not Jewish, Jewish law won’t hold you to its rules. It’s only once you make a commitment to Judaism that you’re truly obligated by the commandments. If Judaism is or is becoming something that you want to take on, a little dolphin on your ankle, (or even a skeleton on your bicep) shouldn’t stop you.