Ignore the doomsayers who may tell you email marketing is dead. Be in no doubt email marketing is alive and well, as are those businesses that use it as part of their overall marketing strategy.
Done correctly email marketing is one of the most effective ways of building a relationship with potential clients and maintaining one with those who have already used your services.
With potential clients, if the email you send them includes useful information related to the services you offer, then when there comes a time that they may actually need to employ a lawyer, then that relationship you have built with them will go long way in their making their decision to employing you to represent them.
For existing clients, they may not require your services again for some time, but by staying in touch you are most likely going to be the lawyer they recommend to their friends, family, and work colleagues should any of them ever need a personal injury lawyer.
To incentivise people to sign up for your emails you could offer them a free report relating to personal injury compensation, for example. This need only be 8 or 9 pages, but it should still be something that is useful and worth reading.
Using an autoresponder service means that the emails can be written and scheduled to be sent well in advance, with the option to send individual broadcast emails should you ever wish to let your email subscribers know about something urgent or important.