THE HIGH COURT  
[2021] IEHC 721  
[Record No. 2019/7672]  
BETWEEN  
CAROLINE CROTTY  
PLAINTIFF  
AND 
SAS, AB AND SWEDAVIA AB  
DEFENDANTS  
JUDGMENT of Ms. Justice Butler delivered on the 18th day of November, 2021  
1. This is a ruling on costs consequent on a judgment delivered by me on 10th June, 2021 
[2021] IEHC 394. In that judgment I acceded to an application made by the second 
defendant to set aside the service upon it of a personal injury summons by the plaintiff 
and to strike out the proceedings against it for want of jurisdiction. The proceedings 
remain extant as against the first defendant. The second defendant now makes an 
application for costs against the plaintiff on the basis that it succeeded in full in its  
application. On the face of it that application is straightforward save for the fact that the 
plaintiff has provided detailed written submissions on costs requesting, firstly, that no 
order be made and, secondly, in the event that an order for the second defendant’s costs 
is made, a further order staying payment so that the issue of recoupment of those costs 
from the first defendant can be dealt with when liability between the plaintiff and the first 
defendant is determined. The first defendant has not mad e any submissions.  
2. I will take these matters in sequence. Although ostensibly the plaintiff argues that no 
order for costs should be made in favour of the second defendant, in reality the bulk of 
her argument is directed at the potential liability of t he first defendant in respect of any 
costs which she may be ordered to pay to the second defendant. No specific reason is 
advanced as to why the court should exercise its discretion against making an award of 
costs to the second defendant and depart from t he normal rule that costs should follow 
the event. Therefore, I think that the second defendant is entitled to an order for the 
costs of this application and of the proceedings against it which have now been struck out 
and I will make such an order.  
3. The more complicated issue concerns the plaintiff’s argument that she is – or may be – 
entitled to recoup those costs from the first defendant under s.78 of the Courts of Justice 
Act 1936. Section 78 which is entitled “Liability of unsuccessful defendant for costs of 
successful defendant”  provides as follows: - 
 “Where, in a civil proceeding in any Court, there are two or more defendants and 
the plaintiff succeeds against one or more of the defendants and fails against the 
others or other of the defendants, it  shall be lawful for the court, if having regard to 
all the circumstances it thinks proper so to do, to order that the defendant or 
defendants against whom the plaintiff has succeeded shall (in addition to the 
plaintiff’s own costs) pay to the plaintiff by  way of recoupment the costs which the 
plaintiff is liable to pay and pays to the defendant or defendants against whom he 
has failed.”  
4. The plaintiff served O’Byrne letters on both defendants on 8th October, 2019. The text of 
the letter sent to the first  defendant included the following passage: - 
 “In the event that it becomes necessary for us to issue proceedings against you 
and/or Swedavia AB and if in those proceedings our client is successful against one 
defendant and unsuccessful against another, th en this letter will be used to apply to 
the court for an order that (in addition to any compensation and/or costs recovered 
by our client) the unsuccessful defendant(s) pay by way of recoupment any costs 
which our client is ordered to pay to any successful  defendant(s).”  
5. An O’Byrne letter is typically sent to prospective defendants in circumstances where a 
plaintiff cannot identify at the outset of proceedings which (or how many) of a number of 
alleged wrongdoers are potentially liable for the damage cau sed to her. The effect of the 
letter is to shift the costs -risk created by the plaintiff having sued unnecessary defendants 
to the defendant(s) ultimately found liable to her. An O’Byrne letter is inextricably linked 
to the jurisdiction of a court under s. 78 to direct that the additional costs incurred by 
virtue of the plaintiff having sued one or more other defendants unsuccessfully (including 
any costs ordered against the plaintiff in favour of that defendant) be recouped from the 
unsuccessful defendant. Of course, it does not follow from the fact that an application 
may be made under s.78, that the court will necessarily exercise the jurisdiction to order 
such recoupment. There may be other factors relating to the case or to the way in which 
the plaintiff  has prosecuted it which would render such an order unfair to the unsuccessful 
defendant.  Nonetheless, the sending of an O’Byrne letter prior to the institution of 
proceedings or at an early stage thereafter does afford an intending plaintiff a measure of  
comfort as regards her potential exposure to costs in the event that she succeeds in her 
proceedings but not as against all defendants.  
6. When the second defendant in this case issued its motion, the plaintiff sent a further 
letter (by email) on 23rd Ma rch, 2021 to the solicitors on behalf of the first defendant 
advising that if the motion succeeded, the plaintiff would rely on her original O’Byrne 
letter to seek a stay on any order for costs to allow the plaintiff apply at the conclusion of 
the proceedi ngs to recoup such costs from the first defendant.  An order for the 
recoupment of costs can be made in respect of either costs which the plaintiff is liable to 
pay or costs which the plaintiff actually pays to the successful defendant.  It is not 
necessar y that the costs order be stayed for the plaintiff to make an application under 
s.78, although of course it will usually be in ease of the plaintiff if it is.  I think the salient 
feature of the email of 23rd March was not so much the indication that the p laintiff 
intended to apply for a stay but the flagging of her underlying intention to make an 
application against the first defendant under s.78.  
7. Finally, the plaintiff relies on the proviso to O.99, r.2(3) of the Rules of the Superior 
Courts. Under tha t rule in normal course the High Court should make an award of costs at 
the conclusion of any interlocutory application save in circumstances “where it is not 
possible justly to adjudicate upon liability for costs on the basis of the interlocutory 
applicat ion”. The plaintiff suggests that a full hearing will be required to establish the 
relevant facts in relation to the first defendant including what the plaintiff characterises as 
“the conduct”  of the first defendant on receipt of the O’Byrne letter. The pl aintiff also 
seeks that the costs incurred by her in unsuccessfully defending the motion should be 
reserved to the trial so that the trial judge may make an order under s.78 should they 
think it proper to do so.  
8. I have considerable difficulty with many aspects of the plaintiff’s submissions. O’Byrne 
letters are a regular feature of litigation particularly in personal injury cases where the 
actions of a number of people may have potentially contributed to the damage ultimately 
suffered by a plaintiff. The  need for an O’Byrne letter may also arise where, as here, it is 
not clear which of two defendants is responsible for the locus in which the accident 
occurred. However, if defendants are to be afforded a fair opportunity to deal with the 
implications of an  O’Byrne letter in the event that they are jointly sued, they must be 
provided with sufficient information by a plaintiff to enable them to assess the claim and 
seek advice on their potential liability.  
9. In this case both defendants raised notices for p articulars seeking to identify where the 
accident occurred. The exact locus of the accident is crucial to the potential allocation of 
liability between the defendants because, as discussed in the main judgment, the first 
defendant is strictly liable under the Montreal Convention for any injury sustained by the 
plaintiff on board or in the course of disembarking the aircraft. Therefore, in order for the 
first defendant to have made an informed decision on receipt of the O’Byrne letter, it was 
necessary for i t to know exactly where the accident is alleged to have occurred to assess 
the extent to which an accident at that location could be said to have happened whilst the 
plaintiff was disembarking the aircraft. It is unrealistic to expect the first defendant t o 
make an informed decision as to whether it should admit liability to the plaintiff or even 
take over conduct of the second defendant’s defence without knowing the basis upon 
which it is claimed that the accident the subject of the proceedings occurred in  the course 
of the plaintiff disembarking the aircraft. The plaintiff had not replied to either notice for 
particulars at the time this motion was heard.  
10. Secondly, the plaintiff has not identified to the court any authority in which an O’Byrne 
letter has been successfully relied upon where the plaintiff’s claim against the successful 
defendant failed because the court did not have jurisdiction to hear it. I note that the test 
generally applied by courts in respect of s.78 is to ask whether it was reaso nable to have 
joined the successful defendant to the proceedings at the outset. In this case the answer 
to that question will depend not on the extent to which, as a matter of Irish tort law, the 
plaintiff could reasonably frame a claim in occupier’s liabi lity against the second defendant 
or the extent to which the circumstances were such that on the basis of the information 
available to her at the outset it was reasonable for the plaintiff to anticipate that the 
second defendant might be liable. Rather it will depend on whether it was reasonable for 
the plaintiff to institute proceedings in Ireland against the second defendant, as the 
occupier of property in Sweden, in light of the existing legal framework.  
11. In my view there is a material difference between the potential costs issues that may 
arise between defendants only one of whom is held liable but both of whom are properly 
sued in the jurisdiction of the court in which the case is to be heard and circumst ances 
where one defendant is able to extract itself from the proceedings because it has not 
been properly sued in this jurisdiction. Clearly, the conduct of the first defendant has not 
caused or contributed to the plaintiff improperly suing the second defe ndant in this 
jurisdiction.  The plaintiff was entitled to make the choice to sue the first defendant in this 
jurisdiction and the first defendant has not contested that decision.  However, it did not 
follow from the plaintiff making that choice that she c ould also sue the second defendant 
in this jurisdiction.  Nothing the first defendant did had any bearing on either the 
plaintiff’s choice or the consequences which flowed from it.  
12. Thirdly, the first defendant was not a party to the second defendant’s  motion against the 
plaintiff. On becoming aware of the motion, the first defendant then served a notice of 
indemnity and contribution against the second defendant, it would seem in ease of the 
plaintiff in an attempt to bring into play Article 8(2) of the  Brussels Recast Regulation 
1215/2012. For the reasons set out in the main judgment, I was not satisfied that this 
could be done in circumstances where proceedings had not been properly served out of 
the jurisdiction on the second defendant in the first pl ace. Counsel appeared on behalf of 
the first defendant at the hearing of the motion to advise the court of the existence of this 
notice of indemnity and contribution and to express a strong preference that all of the 
issues arising out of the plaintiff’s a ccident should be determined in one set of 
proceedings. Thus, broadly speaking, notwithstanding the plaintiff’s characterisation of 
the first defendant as having joined issue with it (in the sense of denying liability), the 
first defendant supported rather  than opposed the plaintiff’s position on the motion.  
Consequently, it is difficult to see why the first defendant should now be liable for the 
costs incurred by the plaintiff in unsuccessfully defending the motion.  
13. I am conscious that the observation s which I have just made are made in circumstances 
where the first defendant has not made any submissions on costs, perhaps because it was 
not formally a party to the motion, although it must have been aware from the email of 
23rd March 2021 that the plain tiff was likely to make an application of this nature. Thus, 
there are potentially serious issues to be determined in the event that the plaintiff 
succeeds against the first defendant and makes an application under s.78 of the 1936 
Act.  It is evident from  the title to s.78 that the intent of the provision is to provide a 
mechanism through which the unsuccessful defendant can be made liable for the costs of 
a successful defendant, albeit that that liability is transferred by ordering the unsuccessful 
defend ant to pay the plaintiff costs which she is liable to pay. This in turn assumes that 
an order will be have been made against the plaintiff in respect of the successful 
defendant’s costs. The mechanism cannot arise if the plaintiff does not succeed against at 
least one defendant.   
14. In all of the circumstances I propose to make the following orders:  
(a) An order that the plaintiff pay the second defendant the costs of this motion. As the 
second defendant is no longer party to the proceedings I do not pro pose staying 
that order until the outcome of the residual proceedings between the plaintiff and 
the first defendant. My decision to refuse a stay is significantly influenced by the 
fact that, as I have held in the main judgment, the second defendant was ne ver 
properly sued in this jurisdiction.  
(b) I will refuse the plaintiff’s application for its costs as against the first defendant.  
The first defendant was not a party to the motion and did not participate at the 
hearing in a manner which was adverse to t he plaintiff’s interests.  
(c) I will direct that the issue of the recoupment of the costs which I have ordered the 
plaintiff pay to the second defendant from the first defendant be reserved to the 
trial of the action.  
(d)  As the first defendant has not m ade an application for its costs, I will make no 
order in that regard.