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T 3072/19: when can a comparative test be used to demonstrate a technical effect?

A recent decision from the EPO Board of Appeal considered whether a comparative test (which was described in the application as filed) could be used to shown an improvement over the prior art. In T 3072/19, independent claim 1 of the main request was directed to an insecticide composition:

“1. Insecticidal aerosol, characterized in that it comprises:
00.1 - 0.5 % by weight of alpha cypermethrin,
00.1 - 0.3 % by weight of permethrin,
0.01 - 0.5 % by weight of tetramethrin,
0.1 - 3.0 % by weight of piperonyl butoxide,
0-0.5 % by weight of a fragrance,
one or more solvents,
one or more propellants, and
0.2 - 0.6 % by weight of a carbamate insecticide.”

The examining division refused the application for lack of inventive step starting from the commercial insecticidal aerosol “ORO”. Claim 1 of the main request differed from ORO in having: (a) alpha cypermethrin in an amount of 0.1-0.5%; and (b) a carbamate insecticide in an amount of 0.2-0.6%.

Applicant’s arguments on appeal

The applicant argued that the examples of the application as filed showed that an insecticidal aerosol according to claim 1 (ARAGON) was more efficient in the control of insects than the commercial aerosol ORO. A summary of results is shown below:

Total efficacy: ARAGON Total efficacy: ORO
Mosquitoes 100% 96.25%
Flies 100% 100%
Cockroaches 74% 26%

According to established jurisprudence, a surprising effect demonstrated in a comparative test can be taken as an indication of inventive step.

Therefore, since the application as filed provided a comparative test which demonstrated greater efficacy compared to the closest prior art the applicant argued that the objective technical problem should be formulated as the provision of an improved insecticidal aerosol.

Decision of the Board of Appeal

Contrary to the applicant’s position, the board found that the comparison done in the examples of the application does not show that the improvement is achieved by the distinguishing features.

This requirement is laid down in numerous decisions. It is also established jurisprudence that, for this purpose, it might be necessary to modify the comparison so that it differs only by such distinguishing feature(s).

The two insecticidal aerosols differed in several respects. In particular, the Board of Appeal noted that, the overall content of active ingredients in ARAGON (above 1.06%) is markedly higher than in ORO (0.80%). The table below summarises the two insecticidal aerosols which were tested in the present case:

0.18% alpha cypermethrin -
0.20% permethrin 0.25% permethrin
0.26% tetramethrin 0.20% tetramethrin
0.42% bendiocarb -
- 0.34% piperonyl butoxide
- 0.01% d-Phenothrin
Total = 1.06% Total = 0.80%

Consequently, the Board of Appeal found that the comparative test cannot show that the improvement has its origin in the distinguishing features of claim 1 (that is, alpha cypermethrin and the carbamate insecticide) because the increased efficacy can be expected merely from the higher amount of active ingredients present.

Thus, there was no technical effect associated with the distinguishing features. The objective technical problem was therefore formulated as merely the provision of an alternative insecticidal aerosol.

In view of the less ambitious technical problem, the Board of Appeal found a lack of inventive step from ORO in combination with D4, which disclosed that a carbamate insecticide and alpha cypermethrin may be combined to form suitable insecticides for aerosol. The board found that the amounts of carbamate insecticide and alpha cypermethrin were not linked to any technical effect and thus amount to an arbitrary selection with no inventive merit.

Lessons for applicants and third parties

This decision is a reminder to applicants that the EPO Boards of Appeal may take a strict approach to comparative tests. Although the applicant compared an insecticidal aerosol according to claim 1 with the closest prior art, the Board of Appeal did not deem this sufficient to demonstrate a technical effect. In other cases, for example during examination, it may be that such comparative tests would be looked upon more favourably.

On the other hand, third parties should take note that even if comparative tests have persuaded the examining division, such tests should be reviewed critically to assess whether a technical effect is convincingly shown to have its origin in the distinguishing feature(s) of the invention or if there are other differences which may account for any technical effect observed.

Considering the present case, one possible way in which the comparative test could have been modified to demonstrate a technical effect is shown below in Comparative Example 1:

ARAGORN Comparative Example 1
0.18% alpha cypermethrin -
0.20% permethrin 0.20% permethrin
0.26% tetramethrin 0.26% tetramethrin
0.42% bendiocarb -
- 0.59% piperonyl butoxide
- 0.01% d-Phenothrin
Total = 1.06% Total = 1.06%

In Comparative Example 1, the overall content of active ingredients is the same, addressing the Board of Appeal’s objection. Additionally, the amounts of permethrin and tetramethrin are the same in both compositions.

If, as in the present case, only “non-ideal” comparative tests are available, then the risks and advantages associated with filing such tests should be carefully considered.

For example, when drafting examples it may be advisable to merely refer to any comparative examples as such, for example, “Comparative Example 1”, to reduce the risk of the comparative example being cited as the closest prior art.

The outcome of the present case may have been different if the applicant had not acknowledged that the comparative example was a commercially available insecticidal aerosol. In that case, the examining division may have found it challenging to establish that the comparative example was prior art.


This decision confirms that the EPO can take a strict approach when considering comparative tests and is a reminder of the potential issues facing applicants when such tests are relied upon.

We recommend seeking advice when designing comparative tests to help ensure that they are suitable for demonstrating a technical effect. For advice or further information please contact your usual D Young and Co representative.

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