Who is Michael McCullough from The Case for Christ and what is their importance?

Michael McCullough is the sixteen-year-old eye witness to the murder of his neighborhood grocer; he knows he has to testify for the murdered man was kind to his family giving them food when they had none. However, the murderer catches up with Michael, his brother and a friend and guns them all down. Michael is the only survivor and becomes the single eyewitness in all three murder cases that puts the defendant in jail for the rest of his life. Strobel uses this evidence to point out that one credible eyewitness's testimony carries a lot of sway.