CHICAGO -- A North Side man is suing the CTA after his 10-year-old son fell through a gap between an "L" train and platform, and then plummeted another 30 feet to the ground below while trying to board a train in 2006.

On July 28, 2006, 10-year-old Andrew Hill and his nanny were standing on an elevated platform at Chicago and Franklin when a northbound train pulled into the station just before 4:15 p.m.

When the doors opened, the two went to board the train, but somehow the boy slipped and fell between the train and platform, according to police.

The boy fell onto Franklin, just south of Chicago Avenue, said Chris Prince, shift manager at the corner Starbucks. He appeared to have landed on his side.

From the street, Prince and others studied the web of steel and wood and couldn't see a gap that seemed large enough for a 4-foot-tall child of average build to fall through.

Witnesses marveled that the boy was alert just minutes after the fall and had no broken bones.

When Andrew fell in the gap between the platform and train, and then fell more than 30 feet onto the ground or street below, it caused serious and permanent injuries, according to a lawsuit filed Wednesday in Cook County Circuit Court. He also suffered psychological injuries.

Nathaniel Hill, of 1660 N. Hudson Ave., filed the negligence suit against the CTA claiming all train cars should have been stopped along a straight portion of track, whereas the train in question was stopped around curves, allowing big enough gaps for someone to fall through.

The suit also alleges the CTA failed to make the area between the platform and where trains stop narrow enough so people could not fall. The CTA was further negligent because, the suit claims, no guards, railing or other means of protection were in place under the tracks to prevent anyone who had fallen in a similar gap to continue to fall all the way to the ground below.

The suit seeks in excess of $50,000 in damages.

Additional information provided by Chicago Sun-Times Inc.