In england-and-wales double jeopardy would not apply as murder is a qualifying offence for a retrial follow an acquittal as per Part 10 and Schedule 5 of the Criminal Justice Act 2003
Part 10, s.75: Cases that may be retried
(1) This Part applies where a person has been acquitted of a
qualifying offence in proceedings—
(a) on indictment in England and Wales,
(b) on appeal against a conviction, verdict or finding in proceedings
on indictment in England and Wales, or
(c) on appeal from a decision on such an appeal.
(2) A person acquitted of an offence in proceedings mentioned in
subsection (1) is treated for the purposes of that subsection as also
acquitted of any qualifying offence of which he could have been
convicted in the proceedings because of the first-mentioned offence
being charged in the indictment, except an offence—
(a) of which he has been convicted,
(b) of which he has been found not guilty by reason of insanity, or
(c) in respect of which, in proceedings where he has been found to be
under a disability (as defined by section 4 of the Criminal Procedure
(Insanity) Act 1964 (c. 84)), a finding has been made that he did the
act or made the omission charged against him.
(3) References in subsections (1) and (2) to a qualifying offence do
not include references to an offence which, at the time of the
acquittal, was the subject of an order under section 77(1) or (3).
(4) This Part also applies where a person has been acquitted, in
proceedings elsewhere than in the United Kingdom, of an offence under
the law of the place where the proceedings were held, if the
commission of the offence as alleged would have amounted to or
included the commission (in the United Kingdom or elsewhere) of a
qualifying offence.
(5) Conduct punishable under the law in force elsewhere than in the
United Kingdom is an offence under that law for the purposes of
subsection (4), however it is described in that law.
(6) This Part applies whether the acquittal was before or after the
passing of this Act.
(7) References in this Part to acquittal are to acquittal in
circumstances within subsection (1) or (4).
(8) In this Part “qualifying offence” means an offence listed in Part 1 of Schedule 5.
Part 1 of Schedule 5: Qualifying offences for purposes of Part 10
[...]
1 Murder.
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Also, if for whatever reason the 2003 Act does not apply then s.54 to s.57 of the Criminal Procedure and Investigations Act 1996 enables the High Court to make an order quashing an acquittal in circumstances where the acquittal resulted from interference with, or intimidation of, a juror or witness (or potential witness). In such circumstances, an acquitted person can be re-tried for the original offence.
s.54 Acquittals tainted by intimidation etc
(1) This section applies where—
(a) a person has been acquitted of an offence, and
(b) a person has been convicted of an administration of justice
offence involving interference with or intimidation of a juror or a
witness (or potential witness) in any proceedings which led to the
acquittal.
(2) Where it appears to the court before which the person was
convicted that—
(a) there is a real possibility that, but for the interference or
intimidation, the acquitted person would not have been acquitted, and
(b) subsection (5) does not apply,
the court shall certify that it so appears.
(3) Where a court certifies under subsection (2) an application may be
made to the High Court for an order quashing the acquittal, and the
Court shall make the order if (but shall not do so unless) the four
conditions in section 55 are satisfied.
(4) Where an order is made under subsection (3) proceedings may be
taken against the acquitted person for the offence of which he was
acquitted.
(5) This subsection applies if, because of lapse of time or for any
other reason, it would be contrary to the interests of justice to take
proceedings against the acquitted person for the offence of which he
was acquitted.
s.55 Conditions for making order
(1) The first condition is that it appears to the High Court likely
that, but for the interference or intimidation, the acquitted person
would not have been acquitted.
(2) The second condition is that it does not appear to the Court that,
because of lapse of time or for any other reason, it would be contrary
to the interests of justice to take proceedings against the acquitted
person for the offence of which he was acquitted.
(3) The third condition is that it appears to the Court that the
acquitted person has been given a reasonable opportunity to make
written representations to the Court.
(4) The fourth condition is that it appears to the Court that the
conviction for the administration of justice offence will stand.
(5) In applying subsection (4) the Court shall—
(a) take into account all the information before it, but
(b) ignore the possibility of new factors coming to light.
(6) Accordingly, the fourth condition has the effect that the Court
shall not make an order under section 54(3) if (for instance) it
appears to the Court that any time allowed for giving notice of appeal
has not expired or that an appeal is pending.