Background

When child sexual exploitation material is seized, digital forensics analysts are required to manually process all “unknown” digital material by determining (a) whether a child is present in the image, and (b) whether the image is of an indecent nature (i.e., illegal).

Objective

The aim of the present study was to (a) assess the reliability with which CSEM is classified as being of an indecent nature, and (b) examine in detail the decision-making process by analysts.

Participants and setting

Five analysts from a specialist unit at a UK police force took part in the study.

Methods

Participants coded a set of 100 images in order to (i) determine the presence of a child, (ii) estimate the approximate age of the child, and (iii) establish the level of severity depicted in accordance with the UK's legal classification system. Qualitative interviews were conducted to develop a better understanding of analysts' decision-making during the process of identifying and analyzing child sexual exploitation material.

Results

Inter-rater reliability analyses revealed that the level of agreement among analysts was moderate to good in terms of age estimation, and very good in terms of image classification. Using thematic analysis, three superordinate themes were identified, namely (i) establishing the presence of a child, (ii) ambiguity of context, and (iii) coding within legal parameters.

Conclusions

A number of specific aspects and features were identified to play a key role in analysts' decision-making process which may be used to inform current developments that aim to partially automate this process.

中文翻译：

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识别和分类儿童性剥削材料的挑战：与数字取证分析师一起进行更生态有效的试点研究

背景

当查获儿童性剥削材料时，数字取证分析师需要通过确定 (a) 图像中是否存在儿童，以及 (b) 图像是否具有不雅性质（即， 非法的）。

客观的

本研究的目的是 (a) 评估 CSEM 被归类为不雅性质的可靠性，以及 (b) 详细检查分析师的决策过程。

参与者和设置

来自英国警察部队专业部门的五名分析师参与了这项研究。

方法

参与者对一组 100 张图像进行编码，以便 (i) 确定儿童的存在，(ii) 估计儿童的大致年龄，以及 (iii) 根据英国的法律分类系统确定所描述的严重程度。进行了定性访谈，以更好地了解分析师在识别和分析儿童性剥削材料的过程中的决策。

结果

评分者间可靠性分析显示，分析师之间的一致性水平在年龄估计方面为中等至良好，在图像分类方面非常好。使用主题分析，确定了三个上级主题，即（i）确定儿童的存在，（ii）上下文的模糊性，以及（iii）在法律参数内编码。

结论

许多特定方面和特征被确定为在分析师的决策过程中发挥关键作用，可用于为旨在部分自动化这一过程的当前发展提供信息。