Originally Posted by Chris Wallace
How? What research? When? Supes didn't say anything about Krypton exploding in his interview with Lois (barring a deleted scene) so Lex had no way of knowing that. And if he did, he had no way of knowing that the fragments had reached Earth. And if he did, he had no way of knowing where they landed. And if he did, he had no way of verifying that it was the same substance. And if he did, he had no way of knowing that the substance was radioactive. And if he did, he had no way of knowing what effect the radiation would have on a Kryptonian. It wasn't like he'd taken samples of kryptonite & tested their effects on Kryptonian DNA. The movie I saw showed Lex just deciding independently that this stuff existed & could kill Superman. You show me where anything different happened.
Lex calculated where Krypton was ("From the precise location in the galaxy he mentions...") makes an informed deduction, ("Krypton exploded in 1948...." I.E, Krypton hasn't been where it was supposed to be,hence it exploded.) and makes a reasonable assumption. ("It is reasonable to assume these particles of debris drifted to earth.")
Having a measure of intelligence,he figures out it would be deadly to him.("The amount of specific radioactivity,to anyone from Krypton,this substance is lethal.") He did enough research to find a piece matching his calculations in Addis Ababa. ("Voila!)
The scene pretty much gives you all the info you need.