I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
It is still in your best interests to have a local attorney represent you. The penalties for hitting a pregnant woman are more harsh than if she weren't, so that fact could actually backfire against you. Once a police report is filed, the whole thing is out of the alleged victim's hand. She doesn't have any legal right to decide not to testify - the district attorney could actually send police to her house to bring her to court to testify. Or the judge could continue the hearing until she can be found (especially if they think you asked her not to come testify or if they believe she's not there because she's afraid of you). If she made up the allegations, she potentially could help you more by going to court and telling the judge that than by disappearing.
It is possible that the hearing will proceed with just the police officer's testimony as to what he saw when he arrived. You'll have the ability to cross examine him to question how well he remembers events. You'll be allowed to argue that, with no witnesses or photographic evidence, they cannot prove the charges against you. Police officers are trained to testify in court, though, and you're not trained to cross-examine witnesses or make arguments, so it could still help to have a lawyer on your side.
The cost of a lawyer varies dramatically based on location, firm size, experience, and other factors, but many criminal lawyers will charge a flat fee for this type of thing. Try calling around to see what different lawyers would charge. If you cannot afford to hire someone, you have a constitutional right to have a judge appoint a lawyer for you at no charge. It is usually to people's benefit to exercise this right.
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