Using a simulated telephone conversation task, we elicited sarcastic production in different utterance types (i.e. declaratives, tag questions and wh-exclamatives from native speakers of the southern variety of British English. Unlike previous studies which focus on static prosodic measurements at the utterance level (e.g. mean pitch, pitch span, intensity), we examined both static prosodic measurements and continuous changes in contour shape in the semantically most important words (or key words) of the sarcastic utterances and their counterparts in the sincere utterances. To this end, we adopted Functional Data Analysis to model pitch variation as contours and represent the contours as continuous function in statistical analysis. We found that sarcasm and sincerity are prosodically distinguishable in the key words alone. The key words in sarcastic utterances are realised with a longer duration and a flatter fall than their counterparts in sincere utterances regardless of utterance type and speaker gender. These results are compatible with previous reports on the use of a smaller pitch span and a slower speech rate in sarcastic utterances than in sincere utterances in North American English. We also observed notable differences in the use of minimum pitch, maximum pitch and contour shape in different utterance types and in the use of mean pitch and duration by male and female speakers. Additionally, we found that the prosody of the key words in sarcastic utterances and their counterparts in sincere utterances has yielded useful predictors for the presence (or absence) of sarcasm in an utterance. Together, our results lend direct support to a key-word–based approach. However, the prosodic predictors included in our analysis alone can achieve only an accuracy of 70.4%, suggesting a need to examine additional prosodic parameters and prosody beyond the key words.