DeWoody

Petitioner seeks a writ of prohibition to restrain the superior court from trying him on a felony charge of driving while under the influence of intoxicating liquor. (Veh. Code, § 23101.) He charges violation of his substantial rights through the ex post facto application of a new statute utilizing blood-alcohol test results as the basis of a presumption that he drove under the.influence of intoxicating liquor.

At its 1969 regular session, the Legislature adopted a bill to add section 23126 to the Vehicle Code, creating a presumption of driving under the influence of intoxicating liquor upon evidence of a prescribed quantum of alcohol in the driver’s blood. The bill was signed by the Governor and filed with the Secretary of State on June 24, 1969, as Statutes of 1969, chapter 231. The legislative session adjourned on September 10, 1969. By force of the referendum provisions of the State Constitution, chapter 231 did not take effect until the 61st day after adjournment, that is, November 10, 1969. (See Cal. Const., art. IV, §§ 8(c), 23.)

The accident giving rise to petitioner’s prosecution occurred on September 4, 1969, after the new presumption law had been approved but…