If defendants can be charged for both the attempted and completed offences, why prefer to indict just the completed offence?

Question

I'm assuming "preferment" means preference, but I don't understand it. s 6(4) assumes that Defendant completed the offence. Why would've Defendant been charged with just the attempted offence? Why only after charging Defendant with attempted offense, would the Crown rather prefer "an indictment for the completed offence"?

Why wouldn't the Crown just charge all Defendants with both the attempted and completed offences from the outset?

Is it possible to convict of an attempt if the attempt was successful?

Is it a defence to a charge of attempt if the defendant in fact succeeded? The answer (not surprisingly) is that the defendant can still be convicted of an attempted offence. Section 6(4) of the Criminal Law Act 1967 resolves the issue:

where a person is charged on an indictment with attempting to commit an offence or with any assault or other act preliminary to an offence, but not with the completed offence, then (subject to the discretion of the court to discharge the jury with a view to the preferment of an indictment for the completed offence) he may be convicted of the offence charged notwithstanding that he is shown to be guilty of the completed offence.³¹

³¹ Webley v Buxton [1977] QB 481 indicates that although s. 6(4) does not apply to summary offences, the common law rule is the same and a defendant can be convicted of an attempt to carry out a summary offence, even if in fact they have committed the full offence.

Herring, Criminal Law: Text, Cases, and Materials (2020 9 ed). p 792.

Answer 1

"Prefer" here doesn't mean preference, it means "to bring or lay" (see sense 5).

So the parenthesized clause could be rephrased as:

The court could decide to discharge the jury, and encourage the Crown to try to indict the person for the completed offense.

As to why the Crown would actually want to charge the attempt instead of the completed offense, there's the obvious point that it saves them the trouble of proving that the offense actually was completed.