Lawyers for Enron Corp. founder Kenneth L. Lay yesterday asked a judge to erase his conviction on fraud and conspiracy charges, citing his death last month before he could appeal a jury verdict. The request signals that Lay's record soon could be wiped clean, seriously complicating the government's attempts to seize his remaining assets. Legal experts explain that the system hesitates to label people guilty if they have not had a chance to appeal and that it is loath to punish dead people or their estates. .