I've certainly found plenty of them when researching nineteenth-century jokes, so they go back at least this far. Here's one I remember from 1891:

Chicago Woman: How much do you charge for a divorce?

Chicago Lawyer: One hundred dollars, ma’am, or six for 500dols

This joke is as much about the loose morals of women from Chicago, but it nicely captures the character of the money-grabbing, amoral lawyer too. It was initially published in an American newspaper, but found its way to Britain (this transatlantic circulation of jokes is my main research interest) - this suggests that the stereotype of the shady lawyer was known in both countries at this time.

I don't have any others to hand, but could soon dig out a few more from the 19th century if you're interested!

One of the more significant lawyer jokes in English literature is from Henry VI pt 2.

"The first thing we do, let's kill all the lawyers."

This comes in the middle of a comic relief section where a fool is making a list of what he would do if he were king.