"The damage is my client feels horrible that Bettie Davis is dead because of the actions he was forced to take," attorney Joe Brodsky told AFP.
"It's affected him greatly. It's a burden he's going to have to carry for the rest of his life."
The December 26 shooting came as the US city was reeling from a series of incidents in which police were accused of being too ready to pull the trigger on their service weapons.
City officials apologized for the death of Davis, a 55-year old mother of five, but have said LeGrier's shooting was justified.
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The city has released few details about the incident except to say that LeGrier was brandishing a baseball bat when he was shot after his father called for help in the wee hours of the morning.
LeGrier, an engineering student who was struggling with mental health problems, had called 911 for help several times earlier that evening but the dispatcher did not send an officer to the house until his father called.
Police tactics and racism have been the subject of a national debate since protests erupted in Ferguson, Missouri, in mid-2014 over the shooting death of a black teenager, 18-year-old Michael Brown.
The US Justice Department is investigating how Chicago police use force after the death of another black teenager, Laquan McDonald, who was shot 16 times as he was walking away from officers.
Brodsky insists this case is nothing like that of McDonald, an incident caught on camera which sparked mass protest and led embattled Mayor Rahm Emanuel to fire Chicago's police chief and reform the department.
"Somebody is swinging a baseball bat and they're two feet above you, you're a pumpkin.