In my younger years, I was a daily user of public transportation. When you need to rely on a bus or a train to get to work or school, you make it your business to commit the transit schedule to memory and before you know it, you are into a daily routine that you rarely, if ever, deviate from. Helen Markham was clearly not a great witness - but she had a job that she had to arrive at within a certain time frame that required her to board a bus that left from her bus stop at a particular time each day - that time was prior to 1:15 - the fact that she was a block away from her bus stop and witnessed the murder at 10th and Patton goes a long way in exonerating Lee Harvey Oswald of the Tippit killing. When you add Markham's testimony about her bus schedule to Bowley's checking of his watch, one cannot come to any conclusion other than the inescapable one that Tippit was killed prior to 1:10 - closer to 1:06 - 1:08 - thus making Oswald's trek from his rooming house to 10th and Patton highly unlikely and perhaps impossible.
