Christopher Johnson was looking forward to getting his taxi back. After Johnson was stabbed and robbed by a passenger, his gray and black cab had been towed by D.C. police and impounded and searched for fingerprints and other evidence.

But when the 67-year-old Johnson picked up his taxi last Thursday from the 3rd Police District on V Street NW, he found something troubling: the knife used in the attack.

"I just opened the door to look in, and I saw something black," Johnson said in an interview Monday at his Southeast Washington home. "I reached down and picked it up. It was the knife. There ain't no doubt about it being the knife because it's got blood on the blade. I don't understand why the police didn't find it."

Johnson said he found the boning knife under the floor mat in the back of the taxi. All but one inch of the blade was missing.

"They kept the car all this time," he said, shaking his head in disbelief. "I told them after the attack what the knife looked like."

Johnson was stabbed in the right eye, nose and left hand shortly after 7 a.m. Nov. 16 after he picked up a fare at Union Station. The man told Johnson to drive him to Dunbar High School in Northwest. But when they arrived, he changed his mind and said he wanted to go to his grandmother's house, around the corner from the school.

When Johnson pulled into the parking lot of an apartment complex at Fourth and O streets NW, the man pulled a stun gun and a knife and demanded money. The two men struggled. Johnson was stabbed several times, but not before he grabbed his attacker's arm and twisted it. The man dropped the knife and ran.

Johnson said he stumbled out of his cab and banged on apartment doors seeking help. When his knocks went unanswered, he drove himself a few blocks to Howard University Hospital, where emergency personnel called police. He now has scars above his eye and on his nose, and he wears a cast on his left hand because the knife pierced the bone.

When police arrived at the hospital, they questioned Johnson and towed his taxi, promising to search for fingerprints and evidence.

Third District Cmdr. Jose Acosta was out of the office yesterday and unavailable for comment. Another police official familiar with the matter said the mobile crime unit that searched the taxi found the broken blade but missed the piece Johnson later discovered.

"The blade was picked up by mobile crime," the official said. "The crime scene search officer who went over the car said he didn't see the handle."

Assistant Chief William P. McManus, who oversees the 1st, 3rd and 5th police districts, attributed the failure to find the knife to "miscommunication." Crime scene search technicians initially searched the taxi and "recovered what they saw in plain view," including most of the knife blade, he said.

The cab was then turned over to mobile crime evidence technicians, who were supposed to dust for fingerprints and look for other evidence.

"There was a miscommunication about who was going to search the car," McManus said yesterday. "Mobile crime assumed the car had been processed by the crime scene search technicians at the district."

McManus acknowledged that the crime scene search technicians were responsible for searching the entire vehicle, which includes looking under the floor mats for evidence.

"There were definitely some shortcomings," he said.

After Johnson found the broken knife, he picked it up and put it in his trunk. Several days passed before he decided to turn it over to police. When Johnson went to the 3rd District station on Tuesday, he couldn't get anyone to take the weapon, McManus acknowledged.

An internal investigation is underway to determine who sent Johnson away without accepting the knife and why the car was not properly searched, McManus said.

"I'm extremely unhappy," McManus said. "This is something that happens all too often. We're going to investigate it to try and find out where the shortcomings are and straighten them out."