Can a defendant appeal against his conviction for a charge of possession of a firearm without obtaining a certificate of probable cause?

These arguments are unavailing. "It has long been established that issues going to the validity of a plea require compliance with section 1237.5. [Citation.] (People v. Panizzon, supra, 13 Cal.4th at p. 76.) Consequently, "irregularities which could be cured, or which would not preclude subsequent proceedings to establish guilt, are waived and may not be asserted on appeal after a guilty plea. [Citation.]" (People v. Turner (1985) 171 Cal.App.3d 116, 126.) Also, an insufficiency-of-the-evidence claim "is not cognizable on appeal, with or without a certificate of probable cause" because "[a] guilty plea `"concedes that the prosecution possesses legally admissible evidence sufficient to prove defendant's guilt beyond a reasonable doubt." [Citation.]'" (People v. Thurman (2007) 157 Cal.App.4th 36, 43.)

But "[n]otwithstanding the broad language of section 1237.5, it is settled that two types of issues may be raised in a guilty . . . plea appeal without issuance of a certificate: (1) search and seizure issues . . .; and (2) issues regarding proceedings held subsequent to the plea for the purpose of determining the degree of the crime and the penalty to be imposed. [Citations.]" (People v. Panizzon, supra, 13 Cal.4th at pp. 74-75.) The present case does not present any issues concerning Fourth Amendment violations. However, defendant's letter brief does challenge the length of his prison sentence describing it as "too much time" and "utterly outrag[e]ous."