Rep. Bill Janklow (search) appears to have had symptoms consistent with a diabetic reaction before his deadly collision with a motorcyclist, an expert testified Friday during the congressman's manslaughter trial.

Dr. Fred Lovrien said he was initially skeptical about a medical defense, but after examining Janklow, reviewing his medical records and discussing his activities in the hours before the crash, he concluded it was possible Janklow had been suffering from low blood sugar, or hypoglycemia (search).

Janklow may not have felt the early symptoms because it was hot when he spoke at an event that morning and because he had had an angry exchange with a heckler, said Lovrien, a defense witness who examined Janklow two months after the crash.

Janklow also said he was taking the medication Atenolol (search), which could hide symptoms of a diabetic reaction, Lovrien said. Atenolol is in a class of drugs called beta-blockers, which affect the heart and circulatory system.

But on cross-examination, deputy prosecutor Roger Ellyson noted that Atenolol was not on the list of medications Janklow said he was taking the day after the Aug. 16 accident and again on Sept. 4.

Lovrien said it would be unwise for any doctor to prescribe such a medication for Janklow because it would worsen his cold-induced asthma (search).

Ellyson also asked Lovrien if it would be unusual for someone to go 20 hours without eating, as several witnesses have said Janklow did on the day of the crash.

"Yes, it would be unusual," Lovrien said. When a diabetic takes insulin but doesn't eat, the person can get fatigued and pass out, according to testimony.

After the cross-examination, Lovrien told Ed Evans, Janklow's lawyer, that his opinion is still that Janklow likely suffered from low blood sugar about the time of the accident -- but only if he had not eaten.

"The one thing that would change it dramatically is if he ate something during the day," Lovrien said.

The defense hopes to prove that Janklow's diabetes (search) was at fault when the congressman sped through a stop sign, putting his Cadillac into the path of motorcyclist Randy Scott, who died after hitting the car.

Prosecutors argue that Janklow made a conscious decision to speed and ignore the stop sign.

Evans had indicated the congressman may take the stand, but he refused to comment Friday on that possibility.

Ellyson had Lovrien read from documents that showed Janklow was twice trained on how to control diabetes.

"I do think as diabetics we need to be personally responsible," Lovrien said in response to a question from Ellyson.

Two neurosurgeons testified Friday for the defense said it would be wise not to believe what Janklow said after the accident, when he said he swerved because of another car.

Dr. Michael Puumala said Janklow "hit his head hard" when the motorcycle struck his car and would have trouble thinking.

The former four-term governor and only congressman from South Dakota could face up to 10 years in prison and a House ethics committee investigation if convicted of second-degree manslaughter.

Senate Democratic leader Tom Daschle (search) testified briefly on Thursday that he did not see Janklow eat anything at an event the two attended the day of the crash. Three other people also testified they didn't see Janklow eat anything.

An emergency medical technician said Janklow didn't appear to be suffering from low blood sugar after the accident, but he said Janklow did accept a Coke and some candy at the scene -- two items that diabetics do not usually take unless they are low on sugar.

Testimony in the case was set to continue Saturday, with closing arguments expected Monday.